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• Distributing cpu-bound compression jobs to multiple computers?

  - by barnaby

  The other day I needed to archive a lot of data on our network and I was frustrated I had no immediate way to harness the power of multiple machines to speed-up the process. I understand that creating a distributed job management system is a leap from a command-line archiving tool. I'm now wondering what the simplest solution to this type of distributed performance scenario could be. Would a custom tool always be a requirement or are there ways to use standard utilities and somehow distribute their load transparently at a higher level? Thanks for any suggestions.

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• Best way to access nested data structures?

  - by Blackshark

  I would like to know what the best way (performance wise) to access a large data structure is. There are about hundred ways to do it but what is the most accessible for the compiler to optimize? One can access a value by foo[someindex].bar[indexlist[i].subelement[j]].baz[0] or create some pointer aliases like sometype_t* tmpfoo = &foo[someindex]; tmpfoo->bar[indexlist[i].subelement[j]].baz[0] or create reference aliases like sometype_t &tmpfoo = foo[someindex]; tmpfoo.bar[indexlist[i].subelement[j]].baz[0] and so forth...

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• Understanding memory leak in Android app.

  - by sat

  After going through few articles about performance, Not able to get this statement exactly. "When a Drawable is attached to a view, the view is set as a callback on the drawable" Soln: "Setting the stored drawables’ callbacks to null when the activity is destroyed." What does that mean, e.g. In my app , I initialize an imageButton in onCreate() like this, imgButton= (ImageButton) findViewById(R.id.imagebtn); At later stage, I get an image from an url, get the stream and convert that to drawable, and set image btn like this, imgButton.setImageDrawable(drawable); According to the above statement, when I am exiting my app, say in onDestroy() I have to set stored drawables’ callbacks to null, not able to understand this part ! In this simple case what I have to set as null ? I am using Android 2.2 Froyo, whether this technique is required, or not necessary.

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• One database or many?

  - by dsims

  I am developing a website that will manage data for multiple entities. No data is shared between entities, but they may be owned by the same customer. A customer may want to manage all their entities from a single "dashboard". So should I have one database for everything, or keep the data seperated into individual databases? Is there a best-practice? What are the positives/negatives for having a: database for the entire site (entity has a "customerID", data has "entityID") database for each customer (data has "entityID") database for each entity (relation of database to customer is outside of database) Multiple databases seems like it would have better performance (fewer rows and joins) but may eventually become a maintenance nightmare.

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• What can we do to make XML processing faster?

  - by adpd

  We work on an internal corporate system that has a web front-end as one of its interfaces. The front-end (Java + Tomcat + Apache) communicates to the back-end (proprietary system written in a COBOL-like language) through SOAP web services. As a result, we pass large XML files back and forth. We believe that this architecture has a significant impact on performance due to the large overhead of XML transportation and parsing. Unfortunately, we are stuck with this architecture. How can we make this XML set-up more efficient? Any tips or techniques are greatly appreciated.

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• Delete from empty table taking forver

  - by Will

  Hello, I have an empty table that previously had a large amount of rows. The table has about 10 columns and indexes on many of them, as well as indexes on multiple columns. DELETE FROM item WHERE 1=1 This takes approximately 40 seconds to complete SELECT * FROM item this takes 4 seconds. The execution plan of SELECT * FROM ITEM shows the following; SQL> select * from midas_item; no rows selected Elapsed: 00:00:04.29 Execution Plan ---------------------------------------------------------- 0 SELECT STATEMENT Optimizer=CHOOSE (Cost=19 Card=123 Bytes=73 80) 1 0 TABLE ACCESS (FULL) OF 'MIDAS_ITEM' (Cost=19 Card=123 Byte s=7380) Statistics ---------------------------------------------------------- 0 recursive calls 0 db block gets 5263 consistent gets 5252 physical reads 0 redo size 1030 bytes sent via SQL*Net to client 372 bytes received via SQL*Net from client 1 SQL*Net roundtrips to/from client 0 sorts (memory) 0 sorts (disk) 0 rows processed any idea why these would be taking so long and how to fix it would be greatly appreciated!!

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• Why do these seemingly similar queries have such drastically different run times?

  - by Jherico

  I'm working with an oracle DB trying to tune some queries and I'm having trouble understanding why working a particular clause in a particular way has such a drastic impact on the query performance. Here is a performant version of the query I'm doing select * from ( select a.*, rownum rn from ( select * from table_foo ) a where rownum < 3 ) where rn >= 2 The same query by replacing the last two lines with this ) a where rownum >=2 rownum < 3 ) performs horribly. Several orders of magnitude worse ) a where rownum between 2 and 3 ) also performs horribly. I don't understand the magic from the first query and how to apply it to further similar queries.

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• Using temporary arrays to cut down on code - inefficient?

  - by tommaisey

  I'm new to c++ (and SO) so sorry if this is obvious. I've started using temporary arrays in my code to cut down on repetition and to make it easier to do the same thing to multiple objects. So instead of: MyObject obj1, obj2, obj3, obj4; obj1.doSomming(arg); obj2.doSomming(arg); obj3.doSomming(arg); obj4.doSomming(arg); I'm doing: MyObject obj1, obj2, obj3, obj4; MyObject* objs[] = {&obj1, &obj2, &obj3, &obj4}; for (int i = 0; i !=4; ++i) objs[i]->doSomming(arg); Is this detrimental to performance? Like, does it cause unnecessary memory allocation? Is it good practice? Thanks.

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• Which of these Array Initializations is better in Ruby?

  - by Bragaadeesh

  Hi, Which of these two forms of Array Initialization is better in Ruby? Method 1: DAYS_IN_A_WEEK = (0..6).to_a HOURS_IN_A_DAY = (0..23).to_a @data = Array.new(DAYS_IN_A_WEEK.size).map!{ Array.new(HOURS_IN_A_DAY.size) } DAYS_IN_A_WEEK.each do |day| HOURS_IN_A_DAY.each do |hour| @data[day][hour] = 'something' end end Method 2: DAYS_IN_A_WEEK = (0..6).to_a HOURS_IN_A_DAY = (0..23).to_a @data = {} DAYS_IN_A_WEEK.each do |day| HOURS_IN_A_DAY.each do |hour| @data[day] ||= {} @data[day][hour] = 'something' end end The difference between the first method and the second method is that the second one does not allocate memory initially. I feel the second one is a bit inferior when it comes to performance due to the numerous amount of Array copies that has to happen. However, it is not straight forward in Ruby to find what is happening. So, if someone can explain me which is better, it would be really great! Thanks

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• How does Array.ForEach() compare to standard for loop in C#?

  - by DaveN59

  I pine for the days when, as a C programmer, I could type: memset( byte_array, '0xFF' ); and get a byte array filled with 'FF' characters. So, I have been looking for a replacement for this: for (int i=0; i < byteArray.Length; i++) { byteArray[i] = 0xFF; } Lately, I have been using some of the new C# features and have been using this approach instead: Array.ForEach<byte>(byteArray, b => b = 0xFF); Granted, the second approach seems cleaner and is easier on the eye, but how does the performance compare to using the first approach? Am I introducing needless overhead by using Linq and generics? Thanks, Dave

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• Faster way of initializing arrays in Delphi

  - by Max

  I'm trying to squeeze every bit of performance in my Delphi application and now I came to a procedure which works with dynamic arrays. The slowest line in it is SetLength(Result, Len); which is used to initialize the dynamic array. When I look at the code for the SetLength procedure I see that it is far from optimal. The call sequence is as follows: _DynArraySetLength - DynArraySetLength DynArraySetLength gets the array length (which is zero for initialization) and then uses ReallocMem which is also unnecessary for initilization. I was doing SetLength to initialize dynamic array all the time. Maybe I'm missing something? Is there a faster way to do this?

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• Small and fast .NET programs? - 65% runtime in ResolvePolicy

  - by forki23

  Hi, I tried to build a very very small .NET app in F#. It just has to convert a small string into another string and print the result to the console like: convert.exe myString == prints something like "myConvertedString" I used dottrace to analyze the performance: 26% (168ms) in my actual string conversion (I thinks this is ok.) 65,80% (425ms) in ResolvePolicy in System.Security.SecurityManager A runtime 500ms on every execution is way too slow. Can I do something to improve this? It would be Ok if only the first call needs this time. Regards, forki

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• New Dell PE R710 - Storage Question

  - by rihatum

  Hi All, Dell PE R710, received from Dell in the following state : Windows Disk 0 1800GB ( Volume C & D ) Windows Disk 1 526 GB (Volume E ) Perc6i Integrated Raid Controller 6 x 500GB Nearline SAS 7200RPM HDDs Raid 5 Configuration with two Virtual Disks I have installed Dell open Manage and it shows the following : Virtual Disk 0 - State : Background Initialization ( 7% ) Virtual Disk 1 - State : Background Initialization ( 25% ) Now when I click on Virtual Disk 0 it shows me all 6 Disks and the same happens when I click on Virtual Disk 1 it displays all 6 disks. But when I click on Storage Perc6i Connector 0 I get 4 Physical disks with the following numbers : Physical Disk 0:0:0 Physical Disk 0:0:1 Physical Disk 0:0:2 Physical Disk 0:0:3 When I click on Storage Perc6i Connector 1 I get 2 Physical Disks Listed in the following way : Physical Disk 1:0:4 Physical Disk 1:0:5 I am a little confused in this description, does this 1:0:4 interprets to Controller1, Disk4. Does this integrated raid card have two controllers coming out of it ? Also, When I first switched on the machine, the boot partition was showing 1GB Available out of 40GB, now its showing 38GB available out of 40GB. Is this because the Virtual Disks are still Initializing ? Any recommendations or suggestions ? Also, this server have 6 x 500GB NearLine SAS Hard drives, what would be a good raid config ? We are planning to use it for Hyper-V with quite a few (7 or 8) virtual servers, your suggestions would be helpful. Also, while the virtual disks are in a initialization state, can I destroy and re-create the raid configuration ? I would have to do it at the BIOS CTRL-M ? Thanks and Regards

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• Reinserted a RAID disk. Defined as foreign. Is import or clear the correct choice?

  - by Petrus

  I have re-inserted a RAID disk, on a DELL server with Windows Server 2008. The drive-status indicator was changing between a green and amber light, and the monitor gave the following message: There are offline or missing virtual drives with preserved cache. Please check the cables and ensure that all drives are present. Press any key to enter the configuration utility. I pressed a key and the PERC 6/I Integrated BIOS Configuration Utility showed that the RAID Status for that disk was Offline. After reinsertion of the disk the monitor is giving the following message: Foreign configuration(s) found on adapter. Press any key to continue or ‘C’ load the configuration utility, or press ‘F’ to import foreign configuration(s) and continue. After checking around on the net I am uncertain if I should choose import or clear. I cannot find out if an import means importing information from the array/system to the now foreign disk or the other way, i.e. importing information from the foreign disk to the array/system that was actually working fine. Also; if clear is a necessary thing to do ahead of a rebuild of that disk, or if clear means to clear the system to somehow make it ready to import the information from the foreign disk to the array/system, which is not what I want. I imagine that making the wrong choice here might be fatal. Please help clearing this out by telling what to choose and why.

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• Cluster Node Recovery Using Second Node in Solaris Cluster

  - by Onur Bingul

  Assumptions:Node 0a is the cluster node that has crashed and could not boot anymore.Node 0b is the node in cluster and in production with services active.Both nodes have their boot disk mirrored via SDS/SVM.We have many options to clone the boot disk from node 0b:- make a copy via network using the ufsdump command and pipe to ufsrestore - make a copy inserting the disk locally on node 0b and creating the third mirror with SDS- make a copy inserting the disk locally on node 0b using dd commandIn this procedure we are going to use dd command (from my experience this is the best option).Bare in mind that in the examples provided we work on Sun Fire V240 systems which have SCSI internal disks. In the case of Fibre Channel (FC) internal disks you must pay attention to the unique identifier, or World Wide Name (WWN), associated with each FC disk (in this case take a look at infodoc #40133 in order to recreate the device tree correctly).Procedure:On node 0b the boot disk is c1t0d0 (c1t1d0 mirror) and this is the VTOC:* Partition  Tag  Flags    Sector     Count    Sector  Mount Directory      0      2    00          0   2106432   2106431      1      3    01    2106432  74630784  76737215      2      5    00          0 143349312 143349311      4      7    00   76737216  50340672 127077887      5      4    00  127077888  14683968 141761855      6      0    00  141761856   1058304 142820159      7      0    00  142820160    529152 143349311We will insert the new disk on node 0b and it will be seen as c1t2d0.1) On node 0b we make a copy via dd from disk c1t0d0s2 to disk c1t2d0s2# dd if=/dev/rdsk/c1t0d0s2 of=/dev/rdsk/c1t2d0s2 bs=8192kA copy of a 72GB disk will take approximately about 45 minutes.Note: as an alternative to make identical copy of root over network follow Document ID: 47498Title: Sun[TM] Cluster 3.0: How to Rebuild a node with Veritas Volume Manager2) Perform an fsck on disk c1t2d0 data slices:   1.  fsck -o f /dev/rdsk/c1t2d0s0 (root)   2.  fsck -o f /dev/rdsk/c1t2d0s4 (/var)   3.  fsck -o f /dev/rdsk/c1t2d0s5 (/usr)   4.  fsck -o f /dev/rdsk/c1t2d0s6 (/globaldevices)3) Mount the root file system in order to edit following files for changing the node name:# mount /dev/dsk/c1t2d0s0 /mntChange the hostname from 0b to 0a:# cd /mnt/etc# vi hosts # vi hostname.bge0 # vi hostname.bge2 # vi nodename 4) Change the /mnt/etc/vfstab from the actual:/dev/md/dsk/d201        -       -       swap    -       no      -/dev/md/dsk/d200        /dev/md/rdsk/d200       /       ufs     1       no      -/dev/md/dsk/d205        /dev/md/rdsk/d205       /usr    ufs     1       no      logging/dev/md/dsk/d204        /dev/md/rdsk/d204       /var    ufs     1       no      logging#/dev/md/dsk/d206       /dev/md/rdsk/d206       /globaldevices  ufs     2       yes     loggingswap    -       /tmp    tmpfs   -       yes     -/dev/md/dsk/d206        /dev/md/rdsk/d206       /global/.devices/node@2 ufs     2       noglobalto this (unencapsulate disk from SDS/SVM):/dev/dsk/c1t0d0s1        -       -       swap    -       no      -/dev/dsk/c1t0d0s0       /dev/rdsk/c1t0d0s0       /       ufs     1       no      -/dev/dsk/c1t0d0s5       /dev/rdsk/c1t0d0s5       /usr    ufs     1       no      logging/dev/dsk/c1t0d0s4       /dev/rdsk/c1t0d0s4       /var    ufs     1       no      logging#/dev/md/dsk/d206       /dev/md/rdsk/d206       /globaldevices  ufs     2       yes     loggingswap    -       /tmp    tmpfs   -       yes     -/dev/dsk/c1t0d0s6       /dev/rdsk/c1t0d0s6       /global/.devices/node@1 ufs     2       no globalIt is important that global device partition (slice 6) in the new vfstab will point to the physical partition of the disk (in our case slice 6).Be careful with the name you use for the new disk. In this case we define it as c1t0d0 because we will insert it as target 0 in node 0a.But this could be different based on the configuration you are working on.5) Remove following entry from /mnt/etc/system (part of unencapsulation procedure):rootdev:/pseudo/md@0:0,200,blk6) Correct the link shared -> ../../global/.devices/node@2/dev/md/shared in order to point to the nodeid of node 0a (in our case nodeid 1):# cd /mnt/dev/mdhow it is now.... node 0b has nodeid 2lrwxrwxrwx   1 root     root          42 Mar 10  2005 shared ->../../global/.devices/node@2/dev/md/shared# rm shared# ln -s ../../global/.devices/node@1/dev/md/shared sharedhow is going to be... with nodeid 1 for node 0alrwxrwxrwx   1 root     root          42 Mar 10  2005 shared ->../../global/.devices/node@1/dev/md/shared7) Change nodeid (in our case from 2 to 1):# cd /mnt/etc/cluster# vi nodeid8) Change the file /mnt/etc/path_to_inst in order to reflect the correct nodeid for node 0a:# cd /mnt/etc# vi path_to_instChange entries from node@2 to node@1 with the vi command ":%s/node@2/node@1/g"9) Write the bootblock to the disk... just in case:# /usr/sbin/installboot /usr/platform/sun4u/lib/fs/ufs/bootblk /dev/rdsk/c1t2d0s0Now the disk is ready to be inserted in node 0a in order to bootup the node.10) Bootup node 0a with command "boot -sx"... this is becasue we need to make some changes in ccr files in order to recreate did environment.11) Modify cluster ccr:# cd /etc/cluster/ccr# rm did_instances# rm did_instances.bak# vi directory - remove the did_instances line.# /usr/cluster/lib/sc/ccradm -i /etc/cluster/ccr/directory # grep ccr_gennum /etc/cluster/ccr/directory ccr_gennum -1 # /usr/cluster/lib/sc/ccradm -i /etc/cluster/ccr/infrastructure # grep ccr_gennum /etc/cluster/ccr/infrastructure ccr_gennum -112) Bring the node 0a down again to the ok prompt and then issue the command "boot -r"Now the node will join the cluster and from scstat and metaset command you can verify functionality. Next step is to encapsulate the boot disk in SDS/SVM and create the mirrors.In our case node 0b has metadevice name starting from d200. For this reason on node 0a we need to create metadevice starting from d100. This is just an example, you can have different names.The important thing to remember is that metadevice boot disks have different names on each node.13) Remove metadevice pointing to the boot and mirror disks (inherit from node 0b):# metaclear -r -f d200# metaclear -r -f d201# metaclear -r -f d204# metaclear -r -f d205# metaclear -r -f d206verify from metastat that no metadevices are set for boot and mirror disks.14) Encapsulate the boot disk:# metainit -f d110 1 1 c1t0d0s0# metainit d100 -m d110# metaroot d10015) Reboot node 0a.16) Create all the metadevice for slices remaining on boot disk# metainit -f d111 1 1 c1t0d0s1# metainit d101 -m d111# metainit -f d114 1 1 c1t0d0s4# metainit d104 -m d114# metainit -f d115 1 1 c1t0d0s5# metainit d105 -m d115# metainit -f d116 1 1 c1t0d0s6# metainit d106 -m d11617) Edit the vfstab in order to specifiy metadevices created:old:/dev/dsk/c1t0d0s1        -       -       swap    -       no      -/dev/md/dsk/d100        /dev/md/rdsk/d100       /       ufs     1       no      -/dev/dsk/c1t0d0s5       /dev/rdsk/c1t0d0s5       /usr    ufs     1       no      logging/dev/dsk/c1t0d0s4       /dev/rdsk/c1t0d0s4       /var    ufs     1       no      logging#/dev/md/dsk/d206       /dev/md/rdsk/d206       /globaldevices  ufs     2       yes     loggingswap    -       /tmp    tmpfs   -       yes     -/dev/dsk/c1t0d0s6       /dev/rdsk/c1t0d0s6       /global/.devices/node@1 ufs      2       no  globalnew:/dev/md/dsk/d101        -       -       swap    -       no      -/dev/md/dsk/d100        /dev/md/rdsk/d100       /       ufs     1       no      -/dev/md/dsk/d105        /dev/md/rdsk/d105       /usr    ufs     1       no      logging/dev/md/dsk/d104        /dev/md/rdsk/d104       /var    ufs     1       no      logging#/dev/md/dsk/106       /dev/md/rdsk/d106       /globaldevices  ufs     2       yes     loggingswap    -       /tmp    tmpfs   -       yes     -/dev/md/dsk/d106        /dev/md/rdsk/d106       /global/.devices/node@1 ufs     2       noglobal18) Reboot node 0a in order to check new SDS/SVM boot configuration.19) Label the mirror disk c1t1d0 with the VTOC of boot disk c1t0d0:# prtvtoc /dev/dsk/c1t0d0s2 > /var/tmp/VTOC_c1t0d0 # fmthard -s /var/tmp/VTOC_c1t0d0 /dev/rdsk/c1t1d0s220) Put DB replica on slice 7 of disk c1t1d0:# metadb -a -c 3 /dev/dsk/c1t1d0s721) Create metadevice for mirror disk c1t1d0 and attach the new mirror side:# metainit d120 1 1 c1t1d0s0# metattach d100 d120# metainit d121 1 1 c1t1d0s1# metattach d101 d121# metainit d124 1 1 c1t1d0s4# metattach d104 d124# metainit d125 1 1 c1t1d0s5# metattach d105 d125# metainit d126 1 1 c1t1d0s6# metattach d106 d126

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• Finding a shared HDD attached to the network from my F-13 machine

  - by Ramy

  Sorry for the slew of n00bie questions, but here is one more. I recently partitioned my 1.5TB harddrive according to this question I then bought this to attach the harddrive to my network. The problem is, how do I navigate to the hard drive to move files over the network to the HDD. should this be moved to serverfault? update: the disk isn't even showing up when i call "fdisk -l" (as root). How can I mount it if I can't even find it? [root@Moonface ~]# /sbin/fdisk -l Disk /dev/sda: 160.0 GB, 160041885696 bytes 255 heads, 63 sectors/track, 19457 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: 0x00018598 Device Boot Start End Blocks Id System /dev/sda1 * 1 64 512000 83 Linux Partition 1 does not end on cylinder boundary. /dev/sda2 64 19458 155777024 8e Linux LVM Disk /dev/dm-0: 53.7 GB, 53687091200 bytes 255 heads, 63 sectors/track, 6527 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 Disk /dev/dm-0 doesn't contain a valid partition table Disk /dev/dm-1: 4764 MB, 4764729344 bytes 255 heads, 63 sectors/track, 579 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 Disk /dev/dm-1 doesn't contain a valid partition table Disk /dev/dm-2: 101.0 GB, 101032394752 bytes 255 heads, 63 sectors/track, 12283 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 Disk /dev/dm-2 doesn't contain a valid partition table

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• How to create partition when growing raid5 with mdadm.

  - by hometoast

  I have 4 drives, 2x640GB, and 2x1TB drives. My array is made up of the four 640GB partitions and the beginning of each drive. I want to replace both 640GB with 1TB drives. I understand I need to 1) fail a disk 2) replace with new 3) partition 4) add disk to array My question is, when I create the new partition on the new 1TB drive, do I create a 1TB "Raid Auto Detect" partition? Or do I create another 640GB partition and grow it later? Or perhaps the same question could be worded: after I replace the drives how to I grow the 640GB raid partitions to fill the rest of the 1TB drive? fdisk info: Disk /dev/sdb: 1000.2 GB, 1000204886016 bytes 255 heads, 63 sectors/track, 121601 cylinders Units = cylinders of 16065 * 512 = 8225280 bytes Disk identifier: 0xe3d0900f Device Boot Start End Blocks Id System /dev/sdb1 1 77825 625129281 fd Linux raid autodetect /dev/sdb2 77826 121601 351630720 83 Linux Disk /dev/sdc: 1000.2 GB, 1000204886016 bytes 255 heads, 63 sectors/track, 121601 cylinders Units = cylinders of 16065 * 512 = 8225280 bytes Disk identifier: 0xc0b23adf Device Boot Start End Blocks Id System /dev/sdc1 1 77825 625129281 fd Linux raid autodetect /dev/sdc2 77826 121601 351630720 83 Linux Disk /dev/sdd: 640.1 GB, 640135028736 bytes 255 heads, 63 sectors/track, 77825 cylinders Units = cylinders of 16065 * 512 = 8225280 bytes Disk identifier: 0x582c8b94 Device Boot Start End Blocks Id System /dev/sdd1 1 77825 625129281 fd Linux raid autodetect Disk /dev/sde: 640.1 GB, 640135028736 bytes 255 heads, 63 sectors/track, 77825 cylinders Units = cylinders of 16065 * 512 = 8225280 bytes Disk identifier: 0xbc33313a Device Boot Start End Blocks Id System /dev/sde1 1 77825 625129281 fd Linux raid autodetect Disk /dev/md0: 1920.4 GB, 1920396951552 bytes 2 heads, 4 sectors/track, 468846912 cylinders Units = cylinders of 8 * 512 = 4096 bytes Disk identifier: 0x00000000

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• recursive grep started at / hangs

  - by Martin

  I have used following grep search pattern on multiple platforms: grep -r -I -D skip 'string_to_match' / For example on FreeBSD 8.0, FreeBSD 6.4 and Debian 6.0(squeeze). Command does a recursive search starting from root directory, assumes that binary files do not have the 'string_to_match' and skips devices, sockets and named pipes. FreeBSD 8.0 and FreeBSD 6.4 use GNU grep version 2.5.1 and Debian 6.0 uses GNU grep version 2.6.3. On FreeBSD 6.4, last information printed to stderr was "grep: /dev/cuad0: Device busy". After this grep just idles as according to "top -m io -o total" the I/O usage of grep is nonexistent. Same behavior is true under FreeBSD 8.0, but last information sent to stderr is "grep: /tmp/.wine-0: Permission denied" on my installation. In case of Debian, last output to stderr is "grep: /proc/sysrq-trigger: Input/output error". If I check the I/O usage of grep process under Debian, it is following: root@Debian:~# iotop -bp 22439 Total DISK READ: 0.00 B/s | Total DISK WRITE: 0.00 B/s TID PRIO USER DISK READ DISK WRITE SWAPIN IO COMMAND 22439 be/4 root 0.00 B/s 0.00 B/s 0.00 % 0.00 % grep -r -I -D skip 10.10.10.99 / Total DISK READ: 0.00 B/s | Total DISK WRITE: 0.00 B/s TID PRIO USER DISK READ DISK WRITE SWAPIN IO COMMAND 22439 be/4 root 0.00 B/s 0.00 B/s 0.00 % 0.00 % grep -r -I -D skip 10.10.10.99 / Total DISK READ: 0.00 B/s | Total DISK WRITE: 0.00 B/s TID PRIO USER DISK READ DISK WRITE SWAPIN IO COMMAND 22439 be/4 root 0.00 B/s 0.00 B/s 0.00 % 0.00 % grep -r -I -D skip 10.10.10.99 / ^Croot@Debian:~# What might cause this? Is there a way to view which file grep is currently processing in case lsof is not present? I'm able to use lsof under Debian and looks like the problematic file name there is "0xc6b2c230 file struct, ty=0, op=0xc0d34120". I'm not sure what this is.. I'm not able to use lsof or fstat under FreeBSD. PS: I know I could use find utility, but this is not the question.

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• Quantifying the Performance of Garbage Collection vs. Explicit Memory Management

  - by EmbeddedProg

  I found this article here: Quantifying the Performance of Garbage Collection vs. Explicit Memory Management http://www.cs.umass.edu/~emery/pubs/gcvsmalloc.pdf In the conclusion section, it reads: Comparing runtime, space consumption, and virtual memory footprints over a range of benchmarks, we show that the runtime performance of the best-performing garbage collector is competitive with explicit memory management when given enough memory. In particular, when garbage collection has five times as much memory as required, its runtime performance matches or slightly exceeds that of explicit memory management. However, garbage collection’s performance degrades substantially when it must use smaller heaps. With three times as much memory, it runs 17% slower on average, and with twice as much memory, it runs 70% slower. Garbage collection also is more susceptible to paging when physical memory is scarce. In such conditions, all of the garbage collectors we examine here suffer order-of-magnitude performance penalties relative to explicit memory management. So, if my understanding is correct: if I have an app written in native C++ requiring 100 MB of memory, to achieve the same performance with a "managed" (i.e. garbage collector based) language (e.g. Java, C#), the app should require 5*100 MB = 500 MB? (And with 2*100 MB = 200 MB, the managed app would run 70% slower than the native app?) Do you know if current (i.e. latest Java VM's and .NET 4.0's) garbage collectors suffer the same problems described in the aforementioned article? Has the performance of modern garbage collectors improved? Thanks.

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• Recover RAID 5 data after created new array instead of re-using

  - by Brigadieren

  Folks please help - I am a newb with a major headache at hand (perfect storm situation). I have a 3 1tb hdd on my ubuntu 11.04 configured as software raid 5. The data had been copied weekly onto another separate off the computer hard drive until that completely failed and was thrown away. A few days back we had a power outage and after rebooting my box wouldn't mount the raid. In my infinite wisdom I entered mdadm --create -f... command instead of mdadm --assemble and didn't notice the travesty that I had done until after. It started the array degraded and proceeded with building and syncing it which took ~10 hours. After I was back I saw that that the array is successfully up and running but the raid is not I mean the individual drives are partitioned (partition type f8 ) but the md0 device is not. Realizing in horror what I have done I am trying to find some solutions. I just pray that --create didn't overwrite entire content of the hard driver. Could someone PLEASE help me out with this - the data that's on the drive is very important and unique ~10 years of photos, docs, etc. Is it possible that by specifying the participating hard drives in wrong order can make mdadm overwrite them? when I do mdadm --examine --scan I get something like ARRAY /dev/md/0 metadata=1.2 UUID=f1b4084a:720b5712:6d03b9e9:43afe51b name=<hostname>:0 Interestingly enough name used to be 'raid' and not the host hame with :0 appended. Here is the 'sanitized' config entries: DEVICE /dev/sdf1 /dev/sde1 /dev/sdd1 CREATE owner=root group=disk mode=0660 auto=yes HOMEHOST <system> MAILADDR root ARRAY /dev/md0 metadata=1.2 name=tanserv:0 UUID=f1b4084a:720b5712:6d03b9e9:43afe51b Here is the output from mdstat cat /proc/mdstat Personalities : [linear] [multipath] [raid0] [raid1] [raid6] [raid5] [raid4] [raid10] md0 : active raid5 sdd1[0] sdf1[3] sde1[1] 1953517568 blocks super 1.2 level 5, 512k chunk, algorithm 2 [3/3] [UUU] unused devices: <none> fdisk shows the following: fdisk -l Disk /dev/sda: 80.0 GB, 80026361856 bytes 255 heads, 63 sectors/track, 9729 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: 0x000bf62e Device Boot Start End Blocks Id System /dev/sda1 * 1 9443 75846656 83 Linux /dev/sda2 9443 9730 2301953 5 Extended /dev/sda5 9443 9730 2301952 82 Linux swap / Solaris Disk /dev/sdb: 750.2 GB, 750156374016 bytes 255 heads, 63 sectors/track, 91201 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: 0x000de8dd Device Boot Start End Blocks Id System /dev/sdb1 1 91201 732572001 8e Linux LVM Disk /dev/sdc: 500.1 GB, 500107862016 bytes 255 heads, 63 sectors/track, 60801 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: 0x00056a17 Device Boot Start End Blocks Id System /dev/sdc1 1 60801 488384001 8e Linux LVM Disk /dev/sdd: 1000.2 GB, 1000204886016 bytes 255 heads, 63 sectors/track, 121601 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: 0x000ca948 Device Boot Start End Blocks Id System /dev/sdd1 1 121601 976760001 fd Linux raid autodetect Disk /dev/dm-0: 1250.3 GB, 1250254913536 bytes 255 heads, 63 sectors/track, 152001 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 Disk /dev/dm-0 doesn't contain a valid partition table Disk /dev/sde: 1000.2 GB, 1000204886016 bytes 255 heads, 63 sectors/track, 121601 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: 0x93a66687 Device Boot Start End Blocks Id System /dev/sde1 1 121601 976760001 fd Linux raid autodetect Disk /dev/sdf: 1000.2 GB, 1000204886016 bytes 255 heads, 63 sectors/track, 121601 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: 0xe6edc059 Device Boot Start End Blocks Id System /dev/sdf1 1 121601 976760001 fd Linux raid autodetect Disk /dev/md0: 2000.4 GB, 2000401989632 bytes 2 heads, 4 sectors/track, 488379392 cylinders Units = cylinders of 8 * 512 = 4096 bytes Sector size (logical/physical): 512 bytes / 512 bytes I/O size (minimum/optimal): 524288 bytes / 1048576 bytes Disk identifier: 0x00000000 Disk /dev/md0 doesn't contain a valid partition table Per suggestions I did clean up the superblocks and re-created the array with --assume-clean option but with no luck at all. Is there any tool that will help me to revive at least some of the data? Can someone tell me what and how the mdadm --create does when syncs to destroy the data so I can write a tool to un-do whatever was done? After the re-creating of the raid I run fsck.ext4 /dev/md0 and here is the output root@tanserv:/etc/mdadm# fsck.ext4 /dev/md0 e2fsck 1.41.14 (22-Dec-2010) fsck.ext4: Superblock invalid, trying backup blocks... fsck.ext4: Bad magic number in super-block while trying to open /dev/md0 The superblock could not be read or does not describe a correct ext2 filesystem. If the device is valid and it really contains an ext2 filesystem (and not swap or ufs or something else), then the superblock is corrupt, and you might try running e2fsck with an alternate superblock: e2fsck -b 8193 Per Shanes' suggestion I tried root@tanserv:/home/mushegh# mkfs.ext4 -n /dev/md0 mke2fs 1.41.14 (22-Dec-2010) Filesystem label= OS type: Linux Block size=4096 (log=2) Fragment size=4096 (log=2) Stride=128 blocks, Stripe width=256 blocks 122101760 inodes, 488379392 blocks 24418969 blocks (5.00%) reserved for the super user First data block=0 Maximum filesystem blocks=0 14905 block groups 32768 blocks per group, 32768 fragments per group 8192 inodes per group Superblock backups stored on blocks: 32768, 98304, 163840, 229376, 294912, 819200, 884736, 1605632, 2654208, 4096000, 7962624, 11239424, 20480000, 23887872, 71663616, 78675968, 102400000, 214990848 and run fsck.ext4 with every backup block but all returned the following: root@tanserv:/home/mushegh# fsck.ext4 -b 214990848 /dev/md0 e2fsck 1.41.14 (22-Dec-2010) fsck.ext4: Invalid argument while trying to open /dev/md0 The superblock could not be read or does not describe a correct ext2 filesystem. If the device is valid and it really contains an ext2 filesystem (and not swap or ufs or something else), then the superblock is corrupt, and you might try running e2fsck with an alternate superblock: e2fsck -b 8193 <device> Any suggestions? Regards!

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• The volume "filesystem root" has only 0 bytes disk space remaining?

  - by radek

  I installed 11.10 ~two weeks ago and run into some strange troubles recently. Installation was on brand new laptop with clear 128GB SSD. I opted for encrypting home directory. Apart from that I accepted defaults during the installation. There is no other OS on my laptop. I had circa 40GB in use when (for the third time) I got to see this very unpleasant window: Twice situation was pretty bad and whole system slowed down considerably. After reboot I could not login to graphical interface (with an error message informing about insufficient space) and had to remove some files from command line first. Third time I still managed to quickly delete some files and it helped. My laptop is mainly work environment: so no torrents, games, just two movies. Only media filling space are ~20GB of pictures, and bunch of pdfs. Working mostly on PostgreSQL & PostGIS, GeoServer and QGIS recently. Although I had lots of opportunities to test and practice my backups I would be extremely grateful if somebody could point me to any potential solutions to this problem. My laptop has been bought just before I installed Ubuntu, and it came without OS. Could that be hardware issue? Or is the encrypted home causing me headaches? Thanks for help! Update: As suggested by @maniat1k, here is current output of fdisk -l: WARNING: GPT (GUID Partition Table) detected on '/dev/sda'! The util fdisk doesn't support GPT. Use GNU Parted. Disk /dev/sda: 160.0 GB, 160041885696 bytes 255 heads, 63 sectors/track, 19457 cylinders, total 312581808 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: 0x00000000 Device Boot Start End Blocks Id System /dev/sda1 1 312581807 156290903+ ee GPT

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• How to get bearable 2D and 3D performance on AMD Radeon HD 6950?

  - by l0b0

  I have had an AMD Radeon HD 6950 (i.e., Cayman series) for a couple years now, and I have tried a lot of combinations of drivers and settings with terrible results. I'm completely at a loss as to how to proceed. The open source driver has much better 2D performance, but it offloads all OpenGL rendering to the CPU. What I've tried so far: All the latest stable Ubuntu releases in the period, plus one Linux Mint release. All the latest stable AMD Catalyst Proprietary Display Drivers, and currently 13.1. The unofficial wiki installation instructions for every Ubuntu version and the semi-official Ubuntu instructions. All the tips and tweaks I could find for Minecraft (Optifine, reducing settings to minimum), VLC (postprocessing at minimum, rendering at native video size), Catalyst Control Center (flipped every lever in there) and X11 (some binary toggles I can no longer remember). Results: Typically 13-15 FPS in Minecraft, 30 max (100+ in Windows with the same driver version). Around 10 FPS in Team Fortress 2 using the official Steam client. Choppy video playback, in Flash and with VLC. CPU use goes through the roof when rendering video (150% for 1080p on YouTube in Chromium, 100% for 1080p H264 in VLC). glxgears shows 12.5 FPS when maximized. fgl_glxgears shows 10 FPS when maximized. Hardware details from lshw: Motherboard ASUS P6X58D-E CPU Intel Core i7 CPU 950 @ 3.07GHz (never overclocked; 64 bit) 6 GB RAM Video card product "Cayman PRO [Radeon HD 6950]", vendor "Hynix Semiconductor (Hyundai Electronics)" 2 x 1920x1200 monitors, both connected with HDMI. I feel I must be missing something absolutely fundamental here. Is there no accelerated support for anything on 64-bit architectures? Does a dual monitor completely mess up the driver? $ fglrxinfo display: :0 screen: 0 OpenGL vendor string: Advanced Micro Devices, Inc. OpenGL renderer string: AMD Radeon HD 6900 Series OpenGL version string: 4.2.11995 Compatibility Profile Context $ glxinfo | grep 'direct rendering' direct rendering: Yes I am currently using the open source driver, with the following results: Full frame rate and low CPU load when playing 1080p video. Black screen (but music in the background) in Team Fortress 2. Similar performance in Minecraft as the Catalyst driver. In hindsight obvious, since both end up offloading the rendering to the CPU. My /var/log/Xorg.0.log after upgrading to AMD Catalyst 13.1. Some possibly important lines: (WW) Falling back to old probe method for fglrx (WW) fglrx: No matching Device section for instance (BusID PCI:0@3:0:1) found The generated xorg.conf. The disabled "monitor" 0-DFP9 is actually an A/V receiver, which sometimes confuses the monitor drivers when turned on/off (but not in Windows). All three "monitor" devices are connected with HDMI. Edit: Chris Carter's suggestion to use the xorg-edgers PPA (Catalyst 13.1) resulted in some improvement, but still pretty bad performance overall: Minecraft stabilizes at 13-17 FPS, but at least the CPU load is "only" at 45-60%. Still 150% CPU use for 1080p video rendering on YouTube in Chromium. Massive improvement for 1080p H264 in VLC: 40-50% CPU use and no visible jitter glxgears performance about doubled to 25-30 FPS when maximized. fgl_glxgears still at ~10 FPS when maximized.

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• Administer, manage, monitor, and fine tune the performance of your Oracle SOA Suite 11g Service Infrastructure and SOA composite applications.

  - by JuergenKress

  Key Features of the book If you are an Oracle SOA suite administrator, then this book is your bible. It gives you everything you need to know about all your tasks and help you to apply what you learn in your everyday life right from the first chapter. The book walks through promoting code across environments, performance tuning the service infrastructure, monitoring the environment, configuring security policies, managing the dehydration store, backing and restoring environments and so on. Packed with real-world examples from authors' own experiences, this books offers a unique insight into Oracle SOA Suite Administration. Detailed description The book begins with an introduction of SOA and quickly moves on to management of SOA composite applications. Readers will learn how to manage composite applications, their deployments and lifecycles. Equipped with this knowledge, readers will be introduced to monitoring and performance tuning SOA Suite, monitoring instances, messages, and composite applications, managing faults and exceptions, configuring audit levels of composite applications to include end-to-end monitoring through the use of extended logging as well as administering and configuring all SOA Suite components. A very important aspect of administration is tuning and optimizing the infrastructure for performance and book offers real work recommendations to monitor and performance tune service engines, the underlying WebLogic server, threads and timeouts, files systems, and composite applications. It also covers detailed administration of individual service components, configuring the infrastructure MBeans using both Oracle Enterprise Manager Fusion Middleware Control and WLST based scripts, migrating worklist preferences and BAM data across environments, setting up Email, LDAP and custom XPath. An administrator is always trusted with troubleshooting and root causing problems in the infrastructure and this book will help you through the troubleshooting approaches as how to identify faults and exception through extended logging and thread dumps and find solutions to common startup problems and deployment issues. The advanced contents of this book explains OWSM security framework and how to secure components deployed to the infrastructure along with the details of all groundwork needed to ready the environment. Last few chapters help you to understand and deal with managing the metadata services repository and dehydration store, backup and recovery and concluding with advanced topics such as silent/scripted installations, cloning, upgrading, patching and high availability installations. Packed with real-world examples, and tips straight from the trench; this book offers insights into SOA Suite administration that you will not find elsewhere. Part of our writing style in this book draws heavily on the philosophy of reuse and as such the book provide an ample of executable SQL queries and WLST scripts that administrators can reuse and extend to perform most of the administration tasks such as monitoring instances, processing times, instance states and perform automatic deployments, tuning, migration, and installation. These scripts are spread over each of the chapters in the book and can also be downloaded from here. The book is available in different formats at the following websites: Paperback and eBook versions & Kindle version. It is available for order and signed copies are available through our web site. SOA & BPM Partner Community For regular information on Oracle SOA Suite become a member in the SOA & BPM Partner Community for registration please visit  www.oracle.com/goto/emea/soa (OPN account required) If you need support with your account please contact the Oracle Partner Business Center. Blog Twitter LinkedIn Mix Forum Technorati Tags: SOA book,SOA Suite Adminsitration,SOA Community,Oracle SOA,Oracle BPM,Community,OPN,Jürgen Kress

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• What is the advantage to using a factor of 1024 instead of 1000 for disk size units?

  - by Joe Z.

  When considering the disk space of a storage medium, normally the computer or operating system will represent it in terms of powers of 1024 - a kilobyte is 1,024 bytes, a megabyte is 1,048,576 bytes, a gigabyte is 1,073,741,824 bytes, and so on. But I don't see any practical reason why this convention was adopted. Usually when disk size is represented in kilo-, mega-, or giga-bytes, it has to be converted into decimal first. In places where a power-of-two byte count actually matters (like the block size on a file system), the size is given in bytes anyway (e.g. 4096 bytes). Was it just a little aesthetic novelty that computer makers decided to adopt, but storage medium vendors decided to disregard? Whenever you buy a hard drive, there's always a disclaimer nowadays that says "One gigabyte means one billion bytes". It would feel like using the binary definition of "gigabyte" would artificially inflate the byte count of a device, making drive-makers have to pack 1.1 terabytes into a drive in order to have it show up as "1 TB", or to simply pack 1 terabyte in and have it show up as "931 GB" (and most of them do the latter). Some people have decided to use units like "KiB" or "MiB" in favour of "KB" and "MB" in order to distinguish the two. But is there any merit to the binary prefixes in the first place? There's probably a bit of old history I'm not aware of on this topic, and if there is, I'm looking for somebody to explain it. (Apologies if this is in the wrong place. I felt that a question on best practice might belong here, but I have faith that it will be migrated to the right place if it's incorrect.)

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• A Disk Read Error Occured. Press CTRL+ALT+DEL to restart

  - by darroosh

  I'm new to linux world. Just downloaded ubuntu and installed it alongside with windows 7 . In grub when I choose ubuntu, it opens with no problem, but when I try to open windows 7, this message appears: A Disk Read Error Occured. Press CTRL+ALT+DEL to restart. I googled for that problem which directed me to download a boot repair tool, when I choose : advanced options / retore MBR --> apply, then restart computer , It boot to win 7 without loading the grub menu. then I opened the live ubuntu from a USB, launched the "boot repair" again, choose : recommended repair , then restart, It returns to the first problem , grub menu appear, from which I can choose only ubuntu , but win 7 show this msg again : A Disk Read Error Occured. Press CTRL+ALT+DEL to restart. I repeated more and more with the same results ... What should I do? I created a boot info summary using the "boot repair tool" if this can help , it's in this URL.

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