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  • Linux RAID: Replacing Failed Drive...permanantly

    - by user137519
    Okay, odd question here. I have a server with RAID 5. A drive failed, in a really physically in a really odd way. On the machine it boots and is seen by the BIOS but...no partition can be seen on the drive consistantly (in and out). 2 out of 3 drives working...I made new spare disk and added it, RAID 5 rebuilt clean. All appears well but...when I reboot it keeps trying to use the 2nd drive which doesn't give any partition data, so of course the RAID 5 gets 2 out of 3...again. The status of my drive is as follows: /dev/sda2:Good /dev/sdb2 (drive has physical problem so no partition data) bad, /dev/sdc2:good /dev/sdd2:good. Every time I reboot the mdadm system seems to keep trying to use /dev/sdb which has physical failure (although spins and is detected). /dev/sdd is the new drive I created. I added /dev/sdd to the raid and it rebuilds the raid but this action isn't memorized upon reboot so it keeps listing /dev/sda and /dev/sdc but doesn't use the perfectly good /dev/sdd until I re-add manually. I've tried removing the dead drive with the mdadm tool, but as it cannot see /dev/sdb paritions it will not fail or remove it (says partition doesn't exist). the /etc/mdadm.conf was automatically made on the original OS install which only lists: DEVICE partitions MAILADDR root ARRAY /dev/md2 super-minor=2 ARRAY /dev/md0 super-minor=0 ARRAY /dev/md1 super-minor=1 Basically just the raids to use on boot. I need to remove this semi-dead drive (/dev/sdb) but I'd prefer to know why this is happening before I do. any ideas or suggestions. I supposed I could attempt to clone/replace /dev/sdb (the partitions on drive show up, then disappear shortly after) but given the partition "chester cat" behaviour this seems risky to me and as I have a working "spare" it seems unnecessary. Thanks in advance for your insight.

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  • Take a regular Windows 7 clone with clonezilla (device-to-image)

    - by Mario De Schaepmeester
    I am unexperienced with cloning software and I've decided to use Clonezilla as it seemed best as freeware. I chose device image and left most options standard. I chose expert mode anyway to see what I could configure, and decided to try the lzop algorithm instead of the default one for compression. The rest was left at default. When Clonezilla asked me which partitions to clone (I chose parts to image), I chose the C:\ drive but Windows 7 also creates a 100MB partition on setup for system files (the actual boot partition?). I copied that into the image as well. The reason I didn't choose disk to image is that I also have a data partition that needs to stay intact. Now I'm simply not sure that this is the way to go, should I ever need to restore my disk image. Will Clonezilla know what to do with both partitions and will Windows 7 work perfectly after restoring? Edit: apparantly a similar question has been asked before. The link to the first article in the answer is not relevant to me since it covers a device-to-device clone. It appears the windows installation disk can repair the 100MB partition. As for Clonezilla, it copies "hidden data after the MBR" by default too. I don't know, I feel I'll be allright whether by restoring the partition with Clonezilla or repairing it with the Windows 7 disk.

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  • After installing Windows 7, I can no longer get to Debian 6 (dual boot)

    - by Jeremy
    I had Debian 6 on my machine (Dell Vostro 260) and used GParted to shrink the partition. I then tried installing Windows 7 on that partition. After Windows 7 installed, I could not choose which OS to run. It would just boot into Windows. I ran GParted again, and saw that Windows created another partition, labeled "System Reserved". That partition had the boot flag set. I tried moving the boot flag to other partitions, including my Debian partition and one with a file system "linux-swap". No option would actually load an OS or anything except for the Windows partition, which is not what I want. Is it worth it to try to fix this installation, or should I start over. I have all my data backed up, so I can easily install from scratch if I need to. If I do start from scratch, which OS should I install first? And then, how do I set up the partitions to install the other OS? Let me know if you have any questions. Thanks for your help.

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  • What should I encrypt in Debian during install?

    - by ianfuture
    I have seen various guides and recommendations on web about how best to do this but nothing that clearly explains the best way and why. So I understand there is a need for part of Debian during install to be un-encrypted on its own partition to allow it to boot. Most info I have seen is call this /boot and set the boot flag. Next I believe the best approach is to create another partition out of all the rest of the disk space, encrypt this, then on top of that create a LVM and then within the LVM create my various partitions , name them , select size, and file system type. Can I include /swap in the encrypted LVM part ? Is this approach sound? If so what are the partitions I should use (this is going to be a minimal server install with a view to install as and when what I need for a dev server)? Finally how does the installer know what to put in each partition I define ? I appreciate there are more than one question but any help and suggestions would be appreciated. If further clarification is needed please mention in the comments . EDIT : 16/3/2010 After Richard Holloways reply I thought it relevant to add this info: The reasons why I want to do this are to explore maximising security on any server install and set up, due to interest in the area of Computer Security and Forensics. Also I am trying to peform the task as if it being performed in an enterprise situation. On a technical matter, once set up and configured with minimal packages and ssh this server will not physically be easy to access so I will only be entering via ssh. (Yes I know why encrypt something no one will ever be able to get their hands on? Because I can and I want to is the simple answer, but see above too).

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  • Wipe free space on LVM-LUKS (dm-crypt) Volume

    - by peter4887
    My three partitions for my system are created with LVM on a LUKS partition (dm-crypt). These are /home, / and swap. The filesystem is ext4. They are encrypted, because they are on my laptop and I don't want that some laptop thieves get my data. But I often share my laptop with other people so they can access my encrypted partitions. I don't want that these people can recover my cache and all the data I deleted. So I'm now trying to wipe all my free space on /home to prevent against recovering with tools like photorec. (one overwrite should do, the need of multiple overwriting is just a rumor) But still I haven't found any solution to wipe this free space successfully. I tried dd if=/dev/zero of=/home/fillitup bs=512 count=[count of free sectiors] so my partition was complete full of data. df /dev/mapper/home said 100% is used and there are 0 sectors available. But I could still recover gigs of data with photorec, although I selected to recover just form the free space. photorec displays: /dev/mapper/home - 340 GB / 317 GiB (RO) , but df displays that the size of /home is just 313G, why are there these differences and what did the 340GB means? It looks like there is a place on my /dev/mapper/home partition, that I can't access to overwrite, but I can access it to recover. I also checked for corrupted sectors, but there aren't any. Maybe this is the space between my existing files? Did anyone knows why I can't wipe my free space with dd, and how I can find the location of the loads of recoverable files, to securely delete them?

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  • Boot stuck at blinking cursor before GRUB - only works via BIOS boot menu

    - by delta1
    I have a new box running Debian Squeeze. Grub is installed on /dev/sda, but when booting up I just get a blinking cursor, before the Grub menu. I can only boot to grub successfully when I choose boot options (during post) and select that specific drive! I have made sure the correct drive is set to boot first in the BIOS. So Grub works, but the system won't boot to that drive automatically? Any ideas on what could cause this? Drives sda/b/c are all 2TB (sda runs the system with b/c as raid device md0) with the following partitions: $ cat /proc/partitions major minor #blocks name 8 0 1953514584 sda 8 1 977 sda1 8 2 9765625 sda2 8 3 6445313 sda3 8 4 1937302627 sda4 8 32 1953514584 sdc 8 16 1953514584 sdb 9 0 1953513424 md0 but # fdisk -l /dev/sda gives WARNING: GPT (GUID Partition Table) detected on '/dev/sda'! The util fdisk doesn't support GPT. Use GNU Parted. Disk /dev/sda: 2000.4 GB, 2000398934016 bytes 255 heads, 63 sectors/track, 243201 cylinders Units = cylinders of 16065 * 512 = 8225280 bytes Sector size (logical/physical): 512 bytes / 512 bytes I/O size (minimum/optimal): 512 bytes / 512 bytes Disk identifier: 0x00000000 Device Boot Start End Blocks Id System /dev/sda1 1 243202 1953514583+ ee GPT Any insight into this strange behaviour would be greatly appreciated.

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  • Best format for hard drive for Windows and Mac?

    - by Neil
    I have a 500 GB USB External Hard Drive. I need four partitions on it, for the following purposes: 160 GB for a bootable backup of my Mac. 160 GB for a bootable backup of my Windows. 11 GB for a bootable Snow Leopard Install Disk Rest as for file storage. Now I need a partition table which will get recognised on both Windows and Mac, without needing extra software on Windows, which will let me keep bootable copies of both OS'es, but let me access the file storage from both OS'es. Currently, I have a GUI Partition Table, with Mac OS Extended (Journaled) Partitions for the two backups, Mac OS Extended for the Install Disk, and NTFS for the file storage. While this gets recognised perfectly on my Mac, thanks to an NTFS for Mac driver from Paragon, when connected to Windows, the drive is detected by the machine (listed in Safely Remove USB), but not recognised in Windows Explorer unless I install MacDrive, which is not feasible for me to install on public Windows Machines I might wanna access my storage area on. Can someone recommend the best combination of formats and software/drivers to get this done seamlessly?

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  • Ubuntu 12.04 can't boot after installing with software RAID 1

    - by Bill
    I've been trying to install Ubuntu with software RAID on my server and there is obviously something that I don't understand about the process. This is the guide that I followed: https://help.ubuntu.com/11.04/serverguide/advanced-installation.html I have two identical 1 TB disks in my server. I went through the initial install process and manually set up my partitions. On each disk I set up: (1) 100 MB partition for EFI boot (I didn't originally have this but added it based on a forum post I found after my original install failed to boot, I ended up with EFIboot since that was what the 'guided partitioning' decided to do) (1) 970 MB partition for / (1) 30 MB partition for swap I then created new RAID 1 disks combining the two partitions, one from each disk, such that each partition is mirrored. I then configured their usage as stated above. After saving the configuration I said yes to boot in a degraded state. The rest of the setup went normally, no errors of any kind. I saw GRUB being installed and again no errors. However, after rebooting the server I get the dreaded 'Insert boot media' and nothing happens. I loaded up the recovery disk and the mdadm configuration looks correct. md0 is my EFIBoot partition md1 is my \ partition using ext4 md2 is my swap partition Running file -s /dev/md0 doesn't indicate that GRUB is there and so I attempted to reinstall GRUB using the recovery disk. I selected the md0 disk and it appeared to install just fine. Running file -s /dev/md1 shows the error needs journal recovery, I'm not sure if that's related or not or how to fix that. Rebooting gives me the same problem, no boot media found. I've searched around the internet but can't figure out what to do next or more importantly how to troubleshoot what exactly is going wrong. Thanks!

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  • Role of MBR in the booting process

    - by pg4421
    I am new to stack overflow. So please correct me if my question seems irrelevant or stupid. I read here in Booting Process : The job of the primary boot loader is to find and load the secondary boot loader (stage 2). It does this by looking through the partition table for an active partition. When it finds an active partition, it scans the remaining partitions in the table to ensure that they're all inactive. When this is verified, the active partition's boot record is read from the device into RAM and executed. The question is that I am having a Hard disk which has two Operating System images windows and ubuntu and hence both partitions in which they reside are active. Then why do we have only one active partition always? (I know that active partition is one of the primary partition but then why we are giving special reference to one primary partition? ) I am confused a bit. Please solve my query. Thank you so much.

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  • Performance of external USB disk with ESXi5

    - by PeterMmm
    I have a new HP DL120 G7 server with ESXi5. One VM is a Win2003 instalation and I have an external USB2.0 drive attached by USB Controller and USB Device. I copy a 4GB file from external USB to server disk. In the VM that takes up to 10 minutes. On a native Win2003 that takes aprox. 3 minutes. I have no explaination for that diference: In any case the bottleneck is the USB connection, much slower than the disks (SAS, RAID1). If the USB connection on the VM would be USB1.1 and not USB2.0 it would take much more time. (The disk performance between server partitions on the VM is correct. - see update) Could be that my native box is extremely fast and the VM is the normal case. ??? Update I try with passtrough and a first run copy the same data in aprox. 7 minutes. Still 2 times slower than the native connection. I also did another messure and the copy between partitions on the same VM takes 3 minutes.

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  • How do I re-configure grub options

    - by Ash
    I've searched this topic and I can't find an article with a plausable solution, to my problem. I installed windows 7 first, with 100gb of disk space. I created the necessary partitions via windows. Then I installed Ubuntu 12.04 on the remaining 400gb of disk space. During the Ubuntu installation I installed the ubuntu boot loader on /dev/sda3 which Windows (as expected never granted me the option pre-boot for which OS I wanted to boot). So I re-installed Ubuntu on that /dev/sda3 partition, overriding the windows 7 loader. Now when I boot windows 7, it runs GNU Grub, so like an infinite loop. How can I reconfigure grub to say: /dev/sda is the bootloader. /dev/sda2 is Windows. /dev/sda3 is Ubuntu. Re-installing windows and my partitions isn't an option, purchasing software for windows isn't an option (theres a reason I use linux, it's not because it's free, because you don't have to install lots of shit to get stuff working, and over-all it's a robust OS).

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  • How can I extend / create a new partition from the following setup?

    - by Kiada
    I'm a little unsure what to do in this situation. When I try to create a new simple volume from the unallocated space I get an error because I already have 4 partitions. I have no option to extend either my C:\ primary partition or the E:\ logical drive. C:\ - Gaming Win7 install. D:\ - Storage Unallocated Space - Would somehow like to install OSX on a partition from this space. E:\ - Software Development Win7 install. I:\ - Ignore this. It's an external 1TB HDD. Do I have any options that do not involve formatting / losing information on either C:\ or E:\? Thank you. Link to visual disk partitioning setup image. Edit: A bit more information regarding partitions. Firstly, the image linked above is a screenshot of Windows 7 partitioning tool, easier to read than text I guess! H:\ System Reserved: 100MB NTFS C:\ 244 GB NTFS Healthy (Page File, Primary Partition) D:\ 294 GB NTFS Healthy (Primary Partition) E:\ 100 GB NTFS Healthy (Boot, Page File, Crash Dump, Logical Drive) Unallocated 292 GB Hope this helps :)

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  • Partition Magic 8 made TrueCrypt partition invisible

    - by gmancoda
    Partition Magic 8 took a dump on my TrueCrypt partition... and I let it happen! And now I am left with cleaning up the mess. In short, my encrypted partition is now invisible. TestDisk analysis says of the disk containing the encrypted partition: "Space conflict between the following two partitions". From the googling and searching on various sites, I have learned the following: Hex editing is beyond me. Partition recovery tools are useless. I am not ready to drop the big bucks for professional help. ... that I should have kept an external backup of the Volume header. Now, to get back the volume header, I am planning on recreating the exact same partitions on a new disk of the exact same model, and then encrypting it with the exact same password/keyfiles, and then exporting its volume header to a file. Finally, I hope to be able to restore this volume header on to my damaged drive. Before I undertake this plan, I would like to know if anyone else out there has tried it and, if so, how successful they were. All other suggestions and tips and welcome!! Thanks.

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  • Does my GetEnumerator cause a deadlock?

    - by Scott Chamberlain
    I am starting to write my first parallel applications. This partitioner will enumerate over a IDataReader pulling chunkSize records at a time from the data-source. TLDR; version private object _Lock = new object(); public IEnumerator GetEnumerator() { var infoSource = myInforSource.GetEnumerator(); //Will this cause a deadlock if two threads lock (_Lock) //use the enumator at the same time? { while (infoSource.MoveNext()) { yield return infoSource.Current; } } } full code protected class DataSourcePartitioner<object[]> : System.Collections.Concurrent.Partitioner<object[]> { private readonly System.Data.IDataReader _Input; private readonly int _ChunkSize; public DataSourcePartitioner(System.Data.IDataReader input, int chunkSize = 10000) : base() { if (chunkSize < 1) throw new ArgumentOutOfRangeException("chunkSize"); _Input = input; _ChunkSize = chunkSize; } public override bool SupportsDynamicPartitions { get { return true; } } public override IList<IEnumerator<object[]>> GetPartitions(int partitionCount) { var dynamicPartitions = GetDynamicPartitions(); var partitions = new IEnumerator<object[]>[partitionCount]; for (int i = 0; i < partitionCount; i++) { partitions[i] = dynamicPartitions.GetEnumerator(); } return partitions; } public override IEnumerable<object[]> GetDynamicPartitions() { return new ListDynamicPartitions(_Input, _ChunkSize); } private class ListDynamicPartitions : IEnumerable<object[]> { private System.Data.IDataReader _Input; int _ChunkSize; private object _ChunkLock = new object(); public ListDynamicPartitions(System.Data.IDataReader input, int chunkSize) { _Input = input; _ChunkSize = chunkSize; } public IEnumerator<object[]> GetEnumerator() { while (true) { List<object[]> chunk = new List<object[]>(_ChunkSize); lock(_Input) { for (int i = 0; i < _ChunkSize; ++i) { if (!_Input.Read()) break; var values = new object[_Input.FieldCount]; _Input.GetValues(values); chunk.Add(values); } if (chunk.Count == 0) yield break; } var chunkEnumerator = chunk.GetEnumerator(); lock(_ChunkLock) //Will this cause a deadlock? { while (chunkEnumerator.MoveNext()) { yield return chunkEnumerator.Current; } } } } IEnumerator IEnumerable.GetEnumerator() { return ((IEnumerable<object[]>)this).GetEnumerator(); } } } I wanted IEnumerable object it passed back to be thread safe (the MSDN example was so I am assuming PLINQ and TPL could need it) will the lock on _ChunkLock near the bottom help provide thread safety or will it cause a deadlock? From the documentation I could not tell if the lock would be released on the yeld return. Also if there is built in functionality to .net that will do what I am trying to do I would much rather use that. And if you find any other problems with the code I would appreciate it.

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  • SQL SERVER – Data Pages in Buffer Pool – Data Stored in Memory Cache

    - by pinaldave
    This will drop all the clean buffers so we will be able to start again from there. Now, run the following script and check the execution plan of the query. Have you ever wondered what types of data are there in your cache? During SQL Server Trainings, I am usually asked if there is any way one can know how much data in a table is stored in the memory cache? The more detailed question I usually get is if there are multiple indexes on table (and used in a query), were the data of the single table stored multiple times in the memory cache or only for a single time? Here is a query you can run to figure out what kind of data is stored in the cache. USE AdventureWorks GO SELECT COUNT(*) AS cached_pages_count, name AS BaseTableName, IndexName, IndexTypeDesc FROM sys.dm_os_buffer_descriptors AS bd INNER JOIN ( SELECT s_obj.name, s_obj.index_id, s_obj.allocation_unit_id, s_obj.OBJECT_ID, i.name IndexName, i.type_desc IndexTypeDesc FROM ( SELECT OBJECT_NAME(OBJECT_ID) AS name, index_id ,allocation_unit_id, OBJECT_ID FROM sys.allocation_units AS au INNER JOIN sys.partitions AS p ON au.container_id = p.hobt_id AND (au.type = 1 OR au.type = 3) UNION ALL SELECT OBJECT_NAME(OBJECT_ID) AS name, index_id, allocation_unit_id, OBJECT_ID FROM sys.allocation_units AS au INNER JOIN sys.partitions AS p ON au.container_id = p.partition_id AND au.type = 2 ) AS s_obj LEFT JOIN sys.indexes i ON i.index_id = s_obj.index_id AND i.OBJECT_ID = s_obj.OBJECT_ID ) AS obj ON bd.allocation_unit_id = obj.allocation_unit_id WHERE database_id = DB_ID() GROUP BY name, index_id, IndexName, IndexTypeDesc ORDER BY cached_pages_count DESC; GO Now let us run the query above and observe the output of the same. We can see in the above query that there are four columns. Cached_Pages_Count lists the pages cached in the memory. BaseTableName lists the original base table from which data pages are cached. IndexName lists the name of the index from which pages are cached. IndexTypeDesc lists the type of index. Now, let us do one more experience here. Please note that you should not run this test on a production server as it can extremely reduce the performance of the database. DBCC DROPCLEANBUFFERS This will drop all the clean buffers and we will be able to start again from there. Now run following script and check the execution plan for the same. USE AdventureWorks GO SELECT UnitPrice, ModifiedDate FROM Sales.SalesOrderDetail WHERE SalesOrderDetailID BETWEEN 1 AND 100 GO The execution plans contain the usage of two different indexes. Now, let us run the script that checks the pages cached in SQL Server. It will give us the following output. It is clear from the Resultset that when more than one index is used, datapages related to both or all of the indexes are stored in Memory Cache separately. Let me know what you think of this article. I had a great pleasure while writing this article because I was able to write on this subject, which I like the most. In the next article, we will exactly see what data are cached and those that are not cached, using a few undocumented commands. Reference: Pinal Dave (http://blog.SQLAuthority.com) Filed under: DMV, Pinal Dave, SQL, SQL Authority, SQL Optimization, SQL Query, SQL Scripts, SQL Server, SQL Tips and Tricks, T SQL, Technology Tagged: SQL DMV

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  • How do I fix a corrupted harddrive after failed upgrade?

    - by Nil
    The problem originated when I was trying to fix this problem. Things went horribly, horribly wrong and I ended up with a new problem altogether. The last thing I did was run sudo apt-get install and that caused my system to freeze. I restarted my computer and it would not boot from the harddrive. I ran a copy of Ubuntu 12.10 from a flashdrive that I had and ran gparted to see if my partitions were all there. It returned this message: Invalid partition table on /dev/sda -- wrong signature 5208. The drive appeared as a 2TiB unallocated drive with an error. The drive had 4 partitions before (plus random unallocated space). There was a fat32 partition, an ext4 partition which contained ubuntu 13.04/13.10 (I don't even know which one at this point), an extended partition which contained a swap partition for my ubuntu partition (I was meaning to move that ubuntu partition into the extended partition, never got around to it), and another partition (I don't remember how I formatted it). I should also mention this is a 1TB harddrive. So in short, I have a corrupted partition table on my primary harddrive from which I boot from, how can I fix this? I tried mounting the drive with sudo mount /dev/sda1 /media/ubuntu then I changed my directory to said folder and tried to list files and this monstrosity happened: $ ls ls: cannot access ??w?j^?.: Input/output error ls: cannot access ??(? ?x?.|: Input/output error ls: cannot access 6W_@?)?._??: Input/output error ls: cannot access HB0v???.A}?: Input/output error ls: cannot access ???.?X: Input/output error ls: cannot access t)?.+?l: Input/output error ls: cannot access ?h@ ?.@ : Input/output error ls: cannot access >? @??.???: Input/output error ls: cannot access m???.??: Input/output error ls: cannot access @ if??a?: Input/output error ls: cannot access ?M!vN$?.??n: Input/output error ls: cannot access ?o? ??.Bm`: Input/output error ls: cannot access ?:I??? M. : Input/output error ls: cannot access W??.??: Input/output error ls: cannot access ?: Input/output error ls: cannot access ?W?s??: Input/output error ls: cannot access ?v?k?.???: Input/output error ls: cannot access 5?$<N??: Input/output error .x????.??i: Input/output error ls: cannot access je????.j?1: Input/output error XjD?.???: Input/output error ls: cannot access W??n???.?: Input/output error ls: cannot access ?^x.$"?: Input/output error ls: cannot access !??*!??j.??: Input/output error ls: cannot access '-??k?^?.???: Input/output error ls: cannot access b?w?w?b.\??: Input/output error ls: cannot access o????"z.??B: Input/output error ls: cannot access ??b?h.?3-: Input/output error ls: cannot access ??.$7: Input/output error ls: cannot access )??K.bk: Input/output error ls: cannot access s??z?.?(?: Input/output error ls: cannot access ?F@?0?.@?: Input/output error .?D: Input/output error .??: Input/output error ls: cannot access?????. @: Input/output error ls: cannot access ?/?? ?.??: No such file or directory ls: cannot access rk?p4q(?.?k: Input/output error This looks promising. This is the output of fdisk -l $ sudo fdisk -l /dev/sda Warning: ignoring extra data in partition table 5 Warning: ignoring extra data in partition table 5 Warning: ignoring extra data in partition table 5 Warning: invalid flag 0x5208 of partition table 5 will be corrected by w(rite) Disk /dev/sda: 2199.0 GB, 2199023132672 bytes 255 heads, 63 sectors/track, 267349 cylinders, total 4294967056 sectors Units = sectors of 1 * 512 = 512 bytes Sector size (logical/physical): 512 bytes / 512 bytes I/O size (minimum/optimal): 512 bytes / 512 bytes Disk identifier: 0x44fdfe06 Device Boot Start End Blocks Id System /dev/sda1 113305600 894715903 390705152 c W95 FAT32 (LBA) /dev/sda2 894715904 1489307647 297295872 83 Linux /dev/sda3 1489309694 1497307135 3998721 5 Extended /dev/sda4 1497309184 1953523711 228107264 7 HPFS/NTFS/exFAT /dev/sda5 ? 3013257822 3688738171 337740175 aa Unknown

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  • Big Data – Data Mining with Hive – What is Hive? – What is HiveQL (HQL)? – Day 15 of 21

    - by Pinal Dave
    In yesterday’s blog post we learned the importance of the operational database in Big Data Story. In this article we will understand what is Hive and HQL in Big Data Story. Yahoo started working on PIG (we will understand that in the next blog post) for their application deployment on Hadoop. The goal of Yahoo to manage their unstructured data. Similarly Facebook started deploying their warehouse solutions on Hadoop which has resulted in HIVE. The reason for going with HIVE is because the traditional warehousing solutions are getting very expensive. What is HIVE? Hive is a datawarehouseing infrastructure for Hadoop. The primary responsibility is to provide data summarization, query and analysis. It  supports analysis of large datasets stored in Hadoop’s HDFS as well as on the Amazon S3 filesystem. The best part of HIVE is that it supports SQL-Like access to structured data which is known as HiveQL (or HQL) as well as big data analysis with the help of MapReduce. Hive is not built to get a quick response to queries but it it is built for data mining applications. Data mining applications can take from several minutes to several hours to analysis the data and HIVE is primarily used there. HIVE Organization The data are organized in three different formats in HIVE. Tables: They are very similar to RDBMS tables and contains rows and tables. Hive is just layered over the Hadoop File System (HDFS), hence tables are directly mapped to directories of the filesystems. It also supports tables stored in other native file systems. Partitions: Hive tables can have more than one partition. They are mapped to subdirectories and file systems as well. Buckets: In Hive data may be divided into buckets. Buckets are stored as files in partition in the underlying file system. Hive also has metastore which stores all the metadata. It is a relational database containing various information related to Hive Schema (column types, owners, key-value data, statistics etc.). We can use MySQL database over here. What is HiveSQL (HQL)? Hive query language provides the basic SQL like operations. Here are few of the tasks which HQL can do easily. Create and manage tables and partitions Support various Relational, Arithmetic and Logical Operators Evaluate functions Download the contents of a table to a local directory or result of queries to HDFS directory Here is the example of the HQL Query: SELECT upper(name), salesprice FROM sales; SELECT category, count(1) FROM products GROUP BY category; When you look at the above query, you can see they are very similar to SQL like queries. Tomorrow In tomorrow’s blog post we will discuss about very important components of the Big Data Ecosystem – Pig. Reference: Pinal Dave (http://blog.sqlauthority.com) Filed under: Big Data, PostADay, SQL, SQL Authority, SQL Query, SQL Server, SQL Tips and Tricks, T SQL

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  • SQL SERVER – Partition Parallelism Support in expressor 3.6

    - by pinaldave
    I am very excited to learn that there is a new version of expressor’s data integration platform coming out in March of this year.  It will be version 3.6, and I look forward to using it and telling everyone about it.  Let me describe a little bit more about what will be so great in expressor 3.6: Greatly enhanced user interface Parallel Processing Bulk Artifact Upgrading The User Interface First let me cover the most obvious enhancements. The expressor Studio user interface (UI) has had some significant work done. Kudos to the expressor Engineering team; the entire UI is a visual masterpiece that is very responsive and intuitive. The improvements are more than just eye candy; they provide significant productivity gains when developing expressor Dataflows. Operator shape icons now include a description that identifies the function of each operator, instead of having to guess at the function by the icon. Operator shapes and highlighting depict the current function and status: Disabled, enabled, complete, incomplete, and error. Each status displays an appropriate message in the message panel with correction suggestions. Floating or docking property panels provide descriptive tool tips for each property as well as auto resize when adjusting the canvas, without having to search Help or the need to scroll around to get access to the property. Progress and status indicators let you know when an operation is working. “No limit” canvas with snap-to-grid allows automatic sizing and accurate positioning when you have numerous operators in the Dataflow. The inline tool bar offers quick access to pan, zoom, fit and overview functions. Selecting multiple artifacts with a right click context allows you to easily manage your workspace more efficiently. Partitioning and Parallel Processing Partitioning allows each operator to process multiple subsets of records in parallel as opposed to processing all records that flow through that operator in a single sequential set. This capability allows the user to configure the expressor Dataflow to run in a way that most efficiently utilizes the resources of the hardware where the Dataflow is running. Partitions can exist in most individual operators. Using partitions increases the speed of an expressor data integration application, therefore improving performance and load times. With the expressor 3.6 Enterprise Edition, expressor simplifies enabling parallel processing by adding intuitive partition settings that are easy to configure. Bulk Artifact Upgrading Bulk Artifact Upgrading sounds a bit intimidating, but it actually is not and it is a welcome addition to expressor Studio. In past releases, users were prompted to confirm that they wanted to upgrade their individual artifacts only when opened. This was a cumbersome and repetitive process. Now with bulk artifact upgrading, a user can easily select what artifact or group of artifacts to upgrade all at once. As you can see, there are many new features and upgrade options that will prove to make expressor Studio quicker and more efficient.  I hope I’m not the only one who is excited about all these new upgrades, and that I you try expressor and share your experience with me. Reference: Pinal Dave (http://blog.sqlauthority.com) Filed under: PostADay, SQL, SQL Authority, SQL Performance, SQL Query, SQL Server, SQL Tips and Tricks, SQLServer, T SQL, Technology

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  • Sparse virtual machine disk image resizing weirdness?

    - by Matt H
    I have a partitioned virtual machine disk image created by vmware. What I want to do is resize that by 10GB. The file size is showing as 64424509440. Or 60GB. So I ran this: dd if=/dev/zero of=./win7.img seek=146800640 count=0 It ran without errors and I can verify the new size is in fact 75161927680 bytes or 70GB. This is where it gets a little odd. I started the guest domain in xen which is a Windows 7 enterprise machine. What I was expecting to see in diskmgmt.msc is 2 partitions. 1 system partition at the start of around 100MB and near 60GB partition (which is C drive) followed by around 10GB of free space. Actually what I saw was a 70GB partition!?! That confused me... so I decided to run the Check Disk which when you set it on the C drive it asks you to reboot so it'll run on boot. So I did that and during the boot it ran the checks. It got all the way through stage 3 and didn't show any errors at all. Looked at the partitions in disk manager and now C drive has shrunk back to 60GB and there is no free space. What gives? Ok, I thought I'd try mounting it under Dom0 and examining it with fdisk. This is what I get when mounted sudo xl block-attach 0 tap:aio:/home/xen/vms/otoy_v1202-xen.img xvda w sudo fdisk -l /dev/xvda Disk /dev/xvda: 64.4 GB, 64424509440 bytes 255 heads, 63 sectors/track, 7832 cylinders Units = cylinders of 16065 * 512 = 8225280 bytes Sector size (logical/physical): 512 bytes / 512 bytes I/O size (minimum/optimal): 512 bytes / 512 bytes Disk identifier: 0x582dfc96 Device Boot Start End Blocks Id System /dev/xvda1 * 1 13 102400 7 HPFS/NTFS Partition 1 does not end on cylinder boundary. /dev/xvda2 13 7833 62810112 7 HPFS/NTFS Note the cylinder boundary comment. When I run sudo cfdisk /dev/xvda I get: FATAL ERROR: Bad primary partition 1: Partition ends in the final partial cylinder Press any key to exit cfdisk So I guess this is a bigger problem than first thought. How can I fix this? EDIT: Oops, the cylinder boundary thing is not a problem at all since disks have used LBA etc. So that threw me for a moment... still the problem exists... Now this output looks a little different. sudo sfdisk -uS -l /dev/xvda Disk /dev/xvda: 7832 cylinders, 255 heads, 63 sectors/track Units = sectors of 512 bytes, counting from 0 Device Boot Start End #sectors Id System /dev/xvda1 * 2048 206847 204800 7 HPFS/NTFS /dev/xvda2 206848 125827071 125620224 7 HPFS/NTFS /dev/xvda3 0 - 0 0 Empty /dev/xvda4 0 - 0 0 Empty BTW: I do have a backup of the image so if you help me mess it up that's ok. EDIT: sudo parted /dev/xvda print free Model: Xen Virtual Block Device (xvd) Disk /dev/xvda: 64.4GB Sector size (logical/physical): 512B/512B Partition Table: msdos Number Start End Size Type File system Flags 32.3kB 1049kB 1016kB Free Space 1 1049kB 106MB 105MB primary ntfs boot 2 106MB 64.4GB 64.3GB primary ntfs 64.4GB 64.4GB 1049kB Free Space Cool. Linux is showing free space is 10GB which is what I expect. The problem is windows isn't seeing this?

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  • Using Solaris zfs + iscsi targets with Oracle VM

    - by wim.coekaerts
    I was playing with my Oracle VM setup and needed some shared storage that was block based. I did not have a storage array available but I did have a solaris box, that I use for Oracle VDI, available. I set up a few iscsi targets on this solaris server and exported them to my 2 Oracle VM servers. Here's how I did this : (1) On the solaris side : # zpool list NAME SIZE USED AVAIL CAP HEALTH ALTROOT rpool 544G 129G 415G 23% ONLINE - I just have a simple zpool, called rpool, on this box. It has plenty of space available for my needs. So I will use rpool and I will create 5 50gb vols : zfs create -V 50G rpool/ovm1 zfs create -V 50G rpool/ovm2 zfs create -V 50G rpool/ovm3 zfs create -V 50G rpool/ovm4 zfs create -V 50G rpool/ovm5 I want to use these volumes for iscsi so I have to enable them as shared iscsi devices : zfs set shareiscsi=on rpool/ovm1 zfs set shareiscsi=on rpool/ovm2 zfs set shareiscsi=on rpool/ovm3 zfs set shareiscsi=on rpool/ovm4 zfs set shareiscsi=on rpool/ovm5 The command iscsitadm list target should list these devices so make sure they show up. # iscsitadm list target Target: rpool/ovm1 iSCSI Name: iqn.1986-03.com.sun:02:896c766c-0943-4da5-d47e-9575b5a0be36 Connections: 2 Target: rpool/ovm2 iSCSI Name: iqn.1986-03.com.sun:02:a3116b46-73e0-e8c2-e80c-9a4f71aff069 Connections: 2 Target: rpool/ovm3 iSCSI Name: iqn.1986-03.com.sun:02:a838c400-2730-c0d6-f2c2-ee186a0261c1 Connections: 2 Target: rpool/ovm4 iSCSI Name: iqn.1986-03.com.sun:02:2e046afb-d66d-4f3f-c5de-8115e0ddd931 Connections: 2 Target: rpool/ovm5 iSCSI Name: iqn.1986-03.com.sun:02:66109fbe-81ac-ef05-f85e-ab8c1f34cb43 Connections: 2 At this point I want to make sure that I have some access control on these devices. To make it easier, I will create an alias for my 2 servers and use the alias for the ACL. get the iqn from the 2 servers on my 2 ovm servers (wcoekaer-srv1, wcoekaer-srv2) get the content of /etc/iscsi/initiatorname.iscsi (for each server) InitiatorName=iqn.1986-03.com.sun:01:2a7526f0ffff On the solaris side create the aliases : iscsitadm create initiator -n iqn.1986-03.com.sun:01:2a7526f0ffff wcoekaer-srv1 iscsitadm create initiator -n iqn.1986-03.com.sun:01:e31b08110f1 wcoekaer-srv5 Add the ACL to the targets : iscsitadm modify target -l wcoekaer-srv1 rpool/ovm1 iscsitadm modify target -l wcoekaer-srv1 rpool/ovm2 iscsitadm modify target -l wcoekaer-srv1 rpool/ovm3 iscsitadm modify target -l wcoekaer-srv1 rpool/ovm4 iscsitadm modify target -l wcoekaer-srv1 rpool/ovm5 iscsitadm modify target -l wcoekaer-srv5 rpool/ovm1 iscsitadm modify target -l wcoekaer-srv5 rpool/ovm2 iscsitadm modify target -l wcoekaer-srv5 rpool/ovm3 iscsitadm modify target -l wcoekaer-srv5 rpool/ovm4 iscsitadm modify target -l wcoekaer-srv5 rpool/ovm5 (2) the Oracle VM side On each server just do 2 simple things : # iscsiadm -m discovery -t sendtargets -p ca-vdi1 where ca-vdi1 is my solaris server name # service iscsi restart When I do cat /proc/partitions on my servers I will see the devices show up # cat /proc/partitions major minor #blocks name 8 0 160836480 sda 8 1 104391 sda1 8 2 3148740 sda2 8 3 1052257 sda3 253 0 6377804 dm-0 253 1 6377804 dm-1 253 2 6377804 dm-2 8 16 52428800 sdb 8 32 52428800 sdc 8 48 52428800 sdd 8 80 52428800 sdf 8 64 52428800 sde These 5 new devices sd[b..f] are shared storage for Oracle VM and can be used to pass through to the VM's as phy: devices or put ocfs2 on it and use as shared filesystem storage for dom0 repositories. I am setting up an 11gR2 rac template (the cool stuff Saar did) so I am using my devices to create a 2 node RAC cluster with phy: devices.

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  • Fresh Ubuntu Install - Grub not loading

    - by Ryan Sharp
    System Ubuntu 12.04 64-bit Windows 7 SP1 Samsung 64GB SSD - OS' Samsung 1TB HDD - Games, /Home, Swap WD 300'ishGB HDD - Backup Okay, so I'm very frustrated, so please excuse me if I miss anything out as my head is clouded by anger and impatience, etc. I'll try me best, though. First of all, I'll explain how I got to my predicament. I finally got my new SSD. I firstly installed Windows, which completed without a hitch. Afterwards, I tried to install Ubuntu, which failed several times due to problems irrelevant to this question, but I mention this to explain my frustrations, sorry. Anyway, I finally installed Ubuntu. However, I chose the 'bootloader' to be installed on the same partition as where I was installing the Ubuntu Root partition, as that was what I believed to be the best choice. It was of my thinking that it was supposed to go on the same partition and on the SSD, which is my OS drive, though with my problem, it apparently was wrong. So I tried to fix it by checking guides and following their directions, but seemed to have messed it up even more. Here is what I receive after I use the fdisk -l command: (I also added explanations for which I used each partition for) Disk /dev/sda: 64.0 GB, 64023257088 bytes 255 heads, 63 sectors/track, 7783 cylinders, total 125045424 sectors Units = sectors of 1 * 512 = 512 bytes Sector size (logical/physical): 512 bytes / 512 bytes I/O size (minimum/optimal): 512 bytes / 512 bytes Disk identifier: 0x324971d1 Device Boot Start End Blocks Id System /dev/sda1 * 2048 206847 102400 7 HPFS/NTFS/exFAT /dev/sda2 208896 48957439 24374272 7 HPFS/NTFS/exFAT /dev/sda3 48959486 125044735 38042625 5 Extended /dev/sda5 48959488 125044735 38042624 83 Linux sda1 --/ Windows Recovery sda2 --/ Windows 7 sda3/5 --/ Ubuntu root [ / ] Disk /dev/sdb: 1000.2 GB, 1000204886016 bytes 255 heads, 63 sectors/track, 121601 cylinders, total 1953525168 sectors Units = sectors of 1 * 512 = 512 bytes Sector size (logical/physical): 512 bytes / 512 bytes I/O size (minimum/optimal): 512 bytes / 512 bytes Disk identifier: 0xc0ee6a69 Device Boot Start End Blocks Id System /dev/sdb1 1024208894 1953523711 464657409 5 Extended /dev/sdb3 * 2048 1024206847 512102400 7 HPFS/NTFS/exFAT /dev/sdb5 1024208896 1939851263 457821184 83 Linux /dev/sdb6 1939853312 1953523711 6835200 82 Linux swap / Solaris sdb3 --/ Partition for Steam games, etc. sdb5 --/ Ubuntu Home [ /home ] sdb6 --/ Ubuntu Swap Partition table entries are not in disk order Disk /dev/sdc: 320.1 GB, 320072933376 bytes 255 heads, 63 sectors/track, 38913 cylinders, total 625142448 sectors Units = sectors of 1 * 512 = 512 bytes Sector size (logical/physical): 512 bytes / 512 bytes I/O size (minimum/optimal): 512 bytes / 512 bytes Disk identifier: 0x292eee23 Device Boot Start End Blocks Id System /dev/sdc1 2048 625141759 312569856 7 HPFS/NTFS/exFAT sdc1 --/ Generic backup I also used a Boot Script that other users suggested, so that I can give more details on my partitions and also where Grub is located... ============================= Boot Info Summary: =============================== => Grub2 (v1.99) is installed in the MBR of /dev/sda and looks at sector 1 of the same hard drive for core.img. core.img is at this location and looks for (,msdos5)/boot/grub on this drive. => Grub2 (v1.99) is installed in the MBR of /dev/sdb and looks at sector 1 of the same hard drive for core.img. core.img is at this location and looks for (,msdos5)/boot/grub on this drive. => Windows is installed in the MBR of /dev/sdc. Now that is weird... Why would Grub2 be installed on both my SSD and HDD? Even weirder is why is Windows on the MBR of my backup hard drive? Nothing I did should have done that... Anyway, here is the entire Output from that script... PASTEBIN So, to summarize what I need: How can I fix my setup so grub loads on startup? How can I clean my partitions to remove unnecessary grubs? What did I do wrong so that I don't do something so daft again? Thank you so much for reading, and I hope you can help me. I've been trying to have a successful setup since Friday, and I'm almost at the point that I'm really tempted to throw my computer out the window due to my frustration.

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  • How to get faster graphics in KVM? VNC is painfully slow with Haiku OS guest, Spice won't install and SDL doesn't work

    - by Don Quixote
    I've been coming up to speed on the Haiku operating system, an Open Source clone of BeOS 5 Pro. I'm using an Apple MacBook Pro as my development machine. Apple's BootCamp BIOS does not support more than four partitions on the internal hard drive. While I can set up extended and logical partitions, doing so will prevent any of the installed operating systems from booting. To run Haiku directly on the iron, I boot it off a USB stick. Using external storage is also helpful because I am perpetually out of filesystem space. While VirtualBox is documented to allow access to physical drives, I could not actually get it to work. Also VirtualBox can only use one of the host CPU's cores. While VB guests can be configured for more than one CPU, they are only emulated. A full build of the Haiku OS takes 4.5 under VB. I had the hope of reducing build times by using KVM instead, but it's not working nearly as well as VirtualBox did. The Linux Kernel Virtual Machine is broken in all manner of fundamental ways as seen from Haiku. But I'm a coder; maybe I could contribute to fixing some of those problems. The first problem I've got is that Haiku's video in virt-manager is quite painfully slow. When I drag Haiku windows around the desktop, they lag quite far behind where my mouse is. It's quite difficult to move a window to a precise position on the screen. Just imagine that the mouse was connected to the window title bar with a really stretchy spring. Also Haiku's mouse lags quite far behind where I have moved it. I found lots of Personal Package Archives that enable Spice from QEMU / KVM at the Ubuntu Personal Package Arhives. I tried a few of the PPAs but none of them worked; with one of them, the command "add-apt-repository" crashed with a traceback. There is a Wiki page about Spice, but it says that it only works on 64-bit. My Early 2006 MacBook Pro is 32-bit. Its Apple Model Identifier is MacBookPro1,1; these use Core Duos NOT Core 2 Duos. I don't mind building a source deb for 32-bit if I can expect it to work. Is there some reason that Spice should be 64-bit only? Does it need features of the x86_64 Instruction Set Architecture that x86 does not have? When I try using SDL from virt-manager, the configuration for Local SDL Window says "Xauth: /home/mike/.Xauthority". When I try to start my guest, virt-manager emits an error. When I Googled the error message, the usual solution was to make ~/.Xauthority readible. However, .Xauthorty does not exist in my home directory. Instead I have a $XAUTHORITY environment variable. There is no way to configure SDL in virt-manager to use $XAUTHORITY instead of ~/.Xauthority. Neither does it work to copy the value of $XAUTHORITY into the file. I am ready to scream, because I've been five fscking days trying to make KVM work for Haiku development. There is a whole lot more that is broken than the slow video. All I really want to do for now is speed up my full builds of Haiku by using "jam -j2" to use both cores in my CPU. I may try Xen next, but the last time I monkeyed with Xen it was far, far more broken than I am finding KVM to be. Just for now, I would be satisfied if there were some way to use my USB stick as a drive in VirtualBox. VB does allow me to configure /dev/sdb as a drive, but it always causes a fatal error when I try to launch the guest. Thank You For Any Advice You Can Give Me. -

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  • MySQL Paritioning performance

    - by Imran Pathan
    Measured performance on key partitioned tables and normal tables separately. But we couldn't find any performance improvement with partitioning. Queries are pruned. Using MySQL 5.1.47 on RHEL 4. Table details: UserUsage - Will have entries for user mobile number and data usage for each date. Mobile number and Date as PRI KEY. UserProfile - Queries prev table and stores summary for each mobile number. Mobile number PRI KEY. CREATE TABLE `UserUsage` ( `Msisdn` decimal(20,0) NOT NULL, `Date` date NOT NULL, . . PRIMARY KEY USING BTREE (`Msisdn`,`Date`) ) ENGINE=InnoDB DEFAULT CHARSET=latin1 PARTITION BY KEY(Msisdn) PARTITIONS 50; CREATE TABLE `UserProfile` ( `Msisdn` decimal(20,0) NOT NULL, . . PRIMARY KEY (`Msisdn`) ) ENGINE=InnoDB DEFAULT CHARSET=latin1 PARTITION BY KEY(Msisdn) PARTITIONS 50; Second table is updated by query select and order by date in first table in a perl program, query is select * from UserUsage where Msisdn=number order by Date desc limit 7 [Process data in perl] update UserProfile values(....) where Msisdn=number explain partition for select, shows row being scanned in a particular partition only. Is something wrong with partition design or queries as partitioning is taking almost same or more time compared to normal tables?

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  • Seeking on a Heap, and Two Useful DMVs

    - by Paul White
    So far in this mini-series on seeks and scans, we have seen that a simple ‘seek’ operation can be much more complex than it first appears.  A seek can contain one or more seek predicates – each of which can either identify at most one row in a unique index (a singleton lookup) or a range of values (a range scan).  When looking at a query plan, we will often need to look at the details of the seek operator in the Properties window to see how many operations it is performing, and what type of operation each one is.  As you saw in the first post in this series, the number of hidden seeking operations can have an appreciable impact on performance. Measuring Seeks and Scans I mentioned in my last post that there is no way to tell from a graphical query plan whether you are seeing a singleton lookup or a range scan.  You can work it out – if you happen to know that the index is defined as unique and the seek predicate is an equality comparison, but there’s no separate property that says ‘singleton lookup’ or ‘range scan’.  This is a shame, and if I had my way, the query plan would show different icons for range scans and singleton lookups – perhaps also indicating whether the operation was one or more of those operations underneath the covers. In light of all that, you might be wondering if there is another way to measure how many seeks of either type are occurring in your system, or for a particular query.  As is often the case, the answer is yes – we can use a couple of dynamic management views (DMVs): sys.dm_db_index_usage_stats and sys.dm_db_index_operational_stats. Index Usage Stats The index usage stats DMV contains counts of index operations from the perspective of the Query Executor (QE) – the SQL Server component that is responsible for executing the query plan.  It has three columns that are of particular interest to us: user_seeks – the number of times an Index Seek operator appears in an executed plan user_scans – the number of times a Table Scan or Index Scan operator appears in an executed plan user_lookups – the number of times an RID or Key Lookup operator appears in an executed plan An operator is counted once per execution (generating an estimated plan does not affect the totals), so an Index Seek that executes 10,000 times in a single plan execution adds 1 to the count of user seeks.  Even less intuitively, an operator is also counted once per execution even if it is not executed at all.  I will show you a demonstration of each of these things later in this post. Index Operational Stats The index operational stats DMV contains counts of index and table operations from the perspective of the Storage Engine (SE).  It contains a wealth of interesting information, but the two columns of interest to us right now are: range_scan_count – the number of range scans (including unrestricted full scans) on a heap or index structure singleton_lookup_count – the number of singleton lookups in a heap or index structure This DMV counts each SE operation, so 10,000 singleton lookups will add 10,000 to the singleton lookup count column, and a table scan that is executed 5 times will add 5 to the range scan count. The Test Rig To explore the behaviour of seeks and scans in detail, we will need to create a test environment.  The scripts presented here are best run on SQL Server 2008 Developer Edition, but the majority of the tests will work just fine on SQL Server 2005.  A couple of tests use partitioning, but these will be skipped if you are not running an Enterprise-equivalent SKU.  Ok, first up we need a database: USE master; GO IF DB_ID('ScansAndSeeks') IS NOT NULL DROP DATABASE ScansAndSeeks; GO CREATE DATABASE ScansAndSeeks; GO USE ScansAndSeeks; GO ALTER DATABASE ScansAndSeeks SET ALLOW_SNAPSHOT_ISOLATION OFF ; ALTER DATABASE ScansAndSeeks SET AUTO_CLOSE OFF, AUTO_SHRINK OFF, AUTO_CREATE_STATISTICS OFF, AUTO_UPDATE_STATISTICS OFF, PARAMETERIZATION SIMPLE, READ_COMMITTED_SNAPSHOT OFF, RESTRICTED_USER ; Notice that several database options are set in particular ways to ensure we get meaningful and reproducible results from the DMVs.  In particular, the options to auto-create and update statistics are disabled.  There are also three stored procedures, the first of which creates a test table (which may or may not be partitioned).  The table is pretty much the same one we used yesterday: The table has 100 rows, and both the key_col and data columns contain the same values – the integers from 1 to 100 inclusive.  The table is a heap, with a non-clustered primary key on key_col, and a non-clustered non-unique index on the data column.  The only reason I have used a heap here, rather than a clustered table, is so I can demonstrate a seek on a heap later on.  The table has an extra column (not shown because I am too lazy to update the diagram from yesterday) called padding – a CHAR(100) column that just contains 100 spaces in every row.  It’s just there to discourage SQL Server from choosing table scan over an index + RID lookup in one of the tests. The first stored procedure is called ResetTest: CREATE PROCEDURE dbo.ResetTest @Partitioned BIT = 'false' AS BEGIN SET NOCOUNT ON ; IF OBJECT_ID(N'dbo.Example', N'U') IS NOT NULL BEGIN DROP TABLE dbo.Example; END ; -- Test table is a heap -- Non-clustered primary key on 'key_col' CREATE TABLE dbo.Example ( key_col INTEGER NOT NULL, data INTEGER NOT NULL, padding CHAR(100) NOT NULL DEFAULT SPACE(100), CONSTRAINT [PK dbo.Example key_col] PRIMARY KEY NONCLUSTERED (key_col) ) ; IF @Partitioned = 'true' BEGIN -- Enterprise, Trial, or Developer -- required for partitioning tests IF SERVERPROPERTY('EngineEdition') = 3 BEGIN EXECUTE (' DROP TABLE dbo.Example ; IF EXISTS ( SELECT 1 FROM sys.partition_schemes WHERE name = N''PS'' ) DROP PARTITION SCHEME PS ; IF EXISTS ( SELECT 1 FROM sys.partition_functions WHERE name = N''PF'' ) DROP PARTITION FUNCTION PF ; CREATE PARTITION FUNCTION PF (INTEGER) AS RANGE RIGHT FOR VALUES (20, 40, 60, 80, 100) ; CREATE PARTITION SCHEME PS AS PARTITION PF ALL TO ([PRIMARY]) ; CREATE TABLE dbo.Example ( key_col INTEGER NOT NULL, data INTEGER NOT NULL, padding CHAR(100) NOT NULL DEFAULT SPACE(100), CONSTRAINT [PK dbo.Example key_col] PRIMARY KEY NONCLUSTERED (key_col) ) ON PS (key_col); '); END ELSE BEGIN RAISERROR('Invalid SKU for partition test', 16, 1); RETURN; END; END ; -- Non-unique non-clustered index on the 'data' column CREATE NONCLUSTERED INDEX [IX dbo.Example data] ON dbo.Example (data) ; -- Add 100 rows INSERT dbo.Example WITH (TABLOCKX) ( key_col, data ) SELECT key_col = V.number, data = V.number FROM master.dbo.spt_values AS V WHERE V.[type] = N'P' AND V.number BETWEEN 1 AND 100 ; END; GO The second stored procedure, ShowStats, displays information from the Index Usage Stats and Index Operational Stats DMVs: CREATE PROCEDURE dbo.ShowStats @Partitioned BIT = 'false' AS BEGIN -- Index Usage Stats DMV (QE) SELECT index_name = ISNULL(I.name, I.type_desc), scans = IUS.user_scans, seeks = IUS.user_seeks, lookups = IUS.user_lookups FROM sys.dm_db_index_usage_stats AS IUS JOIN sys.indexes AS I ON I.object_id = IUS.object_id AND I.index_id = IUS.index_id WHERE IUS.database_id = DB_ID(N'ScansAndSeeks') AND IUS.object_id = OBJECT_ID(N'dbo.Example', N'U') ORDER BY I.index_id ; -- Index Operational Stats DMV (SE) IF @Partitioned = 'true' SELECT index_name = ISNULL(I.name, I.type_desc), partitions = COUNT(IOS.partition_number), range_scans = SUM(IOS.range_scan_count), single_lookups = SUM(IOS.singleton_lookup_count) FROM sys.dm_db_index_operational_stats ( DB_ID(N'ScansAndSeeks'), OBJECT_ID(N'dbo.Example', N'U'), NULL, NULL ) AS IOS JOIN sys.indexes AS I ON I.object_id = IOS.object_id AND I.index_id = IOS.index_id GROUP BY I.index_id, -- Key I.name, I.type_desc ORDER BY I.index_id; ELSE SELECT index_name = ISNULL(I.name, I.type_desc), range_scans = SUM(IOS.range_scan_count), single_lookups = SUM(IOS.singleton_lookup_count) FROM sys.dm_db_index_operational_stats ( DB_ID(N'ScansAndSeeks'), OBJECT_ID(N'dbo.Example', N'U'), NULL, NULL ) AS IOS JOIN sys.indexes AS I ON I.object_id = IOS.object_id AND I.index_id = IOS.index_id GROUP BY I.index_id, -- Key I.name, I.type_desc ORDER BY I.index_id; END; The final stored procedure, RunTest, executes a query written against the example table: CREATE PROCEDURE dbo.RunTest @SQL VARCHAR(8000), @Partitioned BIT = 'false' AS BEGIN -- No execution plan yet SET STATISTICS XML OFF ; -- Reset the test environment EXECUTE dbo.ResetTest @Partitioned ; -- Previous call will throw an error if a partitioned -- test was requested, but SKU does not support it IF @@ERROR = 0 BEGIN -- IO statistics and plan on SET STATISTICS XML, IO ON ; -- Test statement EXECUTE (@SQL) ; -- Plan and IO statistics off SET STATISTICS XML, IO OFF ; EXECUTE dbo.ShowStats @Partitioned; END; END; The Tests The first test is a simple scan of the heap table: EXECUTE dbo.RunTest @SQL = 'SELECT * FROM Example'; The top result set comes from the Index Usage Stats DMV, so it is the Query Executor’s (QE) view.  The lower result is from Index Operational Stats, which shows statistics derived from the actions taken by the Storage Engine (SE).  We see that QE performed 1 scan operation on the heap, and SE performed a single range scan.  Let’s try a single-value equality seek on a unique index next: EXECUTE dbo.RunTest @SQL = 'SELECT key_col FROM Example WHERE key_col = 32'; This time we see a single seek on the non-clustered primary key from QE, and one singleton lookup on the same index by the SE.  Now for a single-value seek on the non-unique non-clustered index: EXECUTE dbo.RunTest @SQL = 'SELECT data FROM Example WHERE data = 32'; QE shows a single seek on the non-clustered non-unique index, but SE shows a single range scan on that index – not the singleton lookup we saw in the previous test.  That makes sense because we know that only a single-value seek into a unique index is a singleton seek.  A single-value seek into a non-unique index might retrieve any number of rows, if you think about it.  The next query is equivalent to the IN list example seen in the first post in this series, but it is written using OR (just for variety, you understand): EXECUTE dbo.RunTest @SQL = 'SELECT data FROM Example WHERE data = 32 OR data = 33'; The plan looks the same, and there’s no difference in the stats recorded by QE, but the SE shows two range scans.  Again, these are range scans because we are looking for two values in the data column, which is covered by a non-unique index.  I’ve added a snippet from the Properties window to show that the query plan does show two seek predicates, not just one.  Now let’s rewrite the query using BETWEEN: EXECUTE dbo.RunTest @SQL = 'SELECT data FROM Example WHERE data BETWEEN 32 AND 33'; Notice the seek operator only has one predicate now – it’s just a single range scan from 32 to 33 in the index – as the SE output shows.  For the next test, we will look up four values in the key_col column: EXECUTE dbo.RunTest @SQL = 'SELECT key_col FROM Example WHERE key_col IN (2,4,6,8)'; Just a single seek on the PK from the Query Executor, but four singleton lookups reported by the Storage Engine – and four seek predicates in the Properties window.  On to a more complex example: EXECUTE dbo.RunTest @SQL = 'SELECT * FROM Example WITH (INDEX([PK dbo.Example key_col])) WHERE key_col BETWEEN 1 AND 8'; This time we are forcing use of the non-clustered primary key to return eight rows.  The index is not covering for this query, so the query plan includes an RID lookup into the heap to fetch the data and padding columns.  The QE reports a seek on the PK and a lookup on the heap.  The SE reports a single range scan on the PK (to find key_col values between 1 and 8), and eight singleton lookups on the heap.  Remember that a bookmark lookup (RID or Key) is a seek to a single value in a ‘unique index’ – it finds a row in the heap or cluster from a unique RID or clustering key – so that’s why lookups are always singleton lookups, not range scans. Our next example shows what happens when a query plan operator is not executed at all: EXECUTE dbo.RunTest @SQL = 'SELECT key_col FROM Example WHERE key_col = 8 AND @@TRANCOUNT < 0'; The Filter has a start-up predicate which is always false (if your @@TRANCOUNT is less than zero, call CSS immediately).  The index seek is never executed, but QE still records a single seek against the PK because the operator appears once in an executed plan.  The SE output shows no activity at all.  This next example is 2008 and above only, I’m afraid: EXECUTE dbo.RunTest @SQL = 'SELECT * FROM Example WHERE key_col BETWEEN 1 AND 30', @Partitioned = 'true'; This is the first example to use a partitioned table.  QE reports a single seek on the heap (yes – a seek on a heap), and the SE reports two range scans on the heap.  SQL Server knows (from the partitioning definition) that it only needs to look at partitions 1 and 2 to find all the rows where key_col is between 1 and 30 – the engine seeks to find the two partitions, and performs a range scan seek on each partition. The final example for today is another seek on a heap – try to work out the output of the query before running it! EXECUTE dbo.RunTest @SQL = 'SELECT TOP (2) WITH TIES * FROM Example WHERE key_col BETWEEN 1 AND 50 ORDER BY $PARTITION.PF(key_col) DESC', @Partitioned = 'true'; Notice the lack of an explicit Sort operator in the query plan to enforce the ORDER BY clause, and the backward range scan. © 2011 Paul White email: [email protected] twitter: @SQL_Kiwi

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  • Replace dual-XP installs with single-XP install and repartition drive?

    - by caeious
    Hello, The Current Situation I have a hard drive that currently is split up like so: Primary Partition C: 9.77 GB NTFS Healthy (System) with XP Pro (in Polish) installed Extended Partition D: 39.82 GB NTFS Healthy (Boot) with XP Pro (in English) installed 6.30 GB Free space When I start my comuter I get a black and white Windows Boot Manager dual boot screen with 2 choices both being Microsoft Windows XP. The first choice is the English version of XP and the second choice is the Polish version of XP. Images of my Computer Management window and Dual Boot screen The Mission What I need to do is get rid of the entire extended partition (D: 39.82 GB & 6.30 free space) and just have the one primary C: drive which I assume will be somewheres around 55 GB big. So in the end I just want XP Pro in English running on my C: drive and no black and white boot screen to show up when starting up my laptop. The Question How do I go about successfully completing The Mission with out making my computer a useless pile of silicon, plastic and metal? UPDATE: So I went ahead and tried to follow Neal's suggestion but hit a wall. I got to a Windows XP Pro install screen that had the 3 following options as well as my drive data: To set up Windows XP on the selected item, press Enter To create a partition in the unpartitioned space, press C To delete the selected partition, press D 57232 MB Disk 0 at Id 0 on bus 0 on atapi [MBR] C: Partition1 [NTFS] 10001 MB ( 4642 MB free ) Unpartitioned space 6448 MB D: Partition2 [NTFS] 40774 MB ( 26225 MB free ) Unpartitioned space 8 MB I figured I would go with the first choice ((To set up Windows XP on the selected item, press Enter)) because I just wanted to set up Windows XP on C: Partition1 (which was preselected) so I pressed Enter which brought me to a screen displaying this message: You chose to install Windows XP on a partition that contains another operating system. Installing Windows XP on this partition might cause the other operating system to function improperly. CAUTION: Installing multiple operating systems on a single partition is not recommended. So this leads me to 2 new questions: How do I get rid of the Windows XP (Polish language) install on C: Partition 1 so that I can cleanly and safely install Windows XP (English language) on it? Neal, is this what you meant by me possibly having to delete the partition that the Windows XP (Polish language) install was located on? Since I have the option to delete partitions with the 3rd choice ((To delete the selected partition, press D)), should I do that on this screen or wait until I have Windows XP (English language) safely installed on C: Partition 1? I have to ask these questions because I have read that it is possibly dangerous to delete hard drive partitions. Just being cautious.

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