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  • How does data I/O takes place on USB Flash Memory ?

    - by user35704
    I want to know how is data I/O takes place on flash drives which are typically EEPROM's . I thought so as I was writing a C Program that involves file handling . For a normal HDD , that would involve returning the file pointer and reading or writing data to the disk which would be done by read/write HEAD . While in EEPROM's there is no read/write head , as it's works on mnemonic commands , So how come does the C file handling program works when I apply it to a file on flash drive ?

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  • Install xenserver on iscsi target

    - by Ghassen Telmoudi
    Is is know that Xen Server is based on CentOS, and it is fact that CentOS can be installed on an ISCSI target flawlessly, but I wanted to install Xen server on an ISCSI target I couldn't find a way. I already tried the latest version of xen server 6.2, and there is no obvious way who to do the installation without a local disk. Does anybody have an idea about the subject, or did someone know how to do it? Please share your experience about this subject.

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  • Allowing Apache in Ubuntu to access files in NTFS hard drive

    - by lyrae
    I have LAMP running in Ubuntu. However, my files are located on a separate NTFS hard drive (/media/shared/mysite/). going to http://localhost gives me a 403 how can i, securely, allow apache to read/write the NTFS disk? 'shared' is currently being mounted when system boots. here's the entry in fstab: /dev/sda1 /media/shared ntfs-3g quiet,defaults,locale=en_US.utf8,umask=000 0 0

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  • How to tune system settings for mongoDB on Linux?

    - by jsh
    Trying to squeeze a lot out of one question here -- please bear with me. Although the MongoDB man pages make several useful recommendations about system settings like ulimit (http://docs.mongodb.org/manual/reference/ulimit/), and other production factors (http://docs.mongodb.org/manual/administration/production-notes/) they seem mysteriously silent on things like virtual memory and swap settings. The closest we get to a hint is that "...the operating system’s virtual memory subsystem manages MongoDB’s memory..." (http://docs.mongodb.org/manual/faq/fundamentals/#does-mongodb-require-a-lot-of-ram). Running the same job - high writes and high reads on about 10,000,000 records in a single collection -- on my 4-processor, 4GB RAM macbook and an 8-core ubuntu box with 64GB RAM I saw dramatically WORSE read performance on the linux box with factory settings, and could hear the disk constantly spinning, indicating high I/O and presumably swapping. Yes, other things were happening on the box, but there was plenty of free RAM, disk space, etc.; furthermore, I did not see evidence that Mongo was expanding to take advantage of all that free RAM as it is touted to do. Linux box default settings were as follows: vm.swappiness =60 vm.dirty_background_ratio = 10 vm.dirty_ratio = 20 vm.dirty_expire_centisecs =3000 vm.dirty_writeback_centisecs=500 I hazarded some guesses looking at docs and blogs for other types of databases (Oracle, MYSQL, etc.), experimented, and adjusted as below. vm.swappiness=10 vm.dirty_background_ratio=5 vm.dirty_ratio=5 vm.dirty_writeback_centisecs=250 vm.dirty_expire_centisecs=500 I saw some immediate apparent improvements in read time. However, when I ran my test jobs again, read performance continued to be painfully sluggish during heavy writes. Then, I REBUILT the collection from an available data source - and suddenly I can read at 1ms or less per record WHILE doing the write job! So the question is really two-fold: 1) What are appropriate VM settings for MongoDB on Linux? 2) (bonus) Does Mongo do some checking or optimization with the OS while data is being built? In other words, if I have built a large data set with suboptimal VM or I/O settings, does Mongo make assumptions during the memory-mapping process that will fail to take advantage of optimizations down the road? Obviously I don't fully grok memory mapping under the hood (I was hoping I wouldn't have to). Any help appreciated...thanks! -j

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  • New harddrives failing within weeks.

    - by Jason Kealey
    I've experienced 8 hard disk failures in 3 months and have tried many things to solve the issue permanently but I have failed. I would like to know if you have any advice for me. System was running Win XP on an Asus P5W-DH Deluxe. I have setup a RAID-1 array. I started out with 2 x 500 GB 7200RPM Western Digital drives. One died. I took it out to RMA it. On the same day, the router was fried. Assumed a power surge occurred; connected an older UPS to protect the system. Once I got my hands on an identical disk, I installed it. The RAID array was rebuilt. A few days later, the other one died. Assumed the rebuild caused it to fail. Took it out for RMA. Before the other one arrived, the remaining one died. I then discovered I could re-enable them using the Intel Matrix Storage Manager. I re-enabled both and the system seemed fine for a week, until both died again. I got two new 1.5 TB 7200RPM Seagate drives and re-installed Windows 7. Also replaced the UPS and power supply. They both died again. The voltage on the plug is stable between 120 and 122V as per the UPS. None of the other devices have had any problems (monitors, etc.). At this point, I see two options: a) electrical issue in the house that was, for some reason, not blocked by the UPS. b) something else inside the system causing surges? motherboard? onboard raid controller? Failures happen fairly quickly, between 2 and 14 days after I fix the previous issue. I just gotten a new computer (Core i7) to replace it. If it is stable, I can determine that b) was the problem. If it fries its hard drive again, I can determine that it is an electrical issue in the house. Do you have any other thoughts? Any tools I can run on the drives that failed to get more information about the original SMART event history?

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  • MS Publisher 2003 - hangs when saving to desktop

    - by Chris
    We have a win 7 home prem pc, amd cpu, 8G ram, plenty of free disk space. Whenever user is working in publisher 20003, and tries to save a publisher 2003 document to the desktop, the save as dialog hangs and takes 2-3 minutes to display the desktop save location. I've tested excel 2003, it has no problems immediately displaying the desktop save as location and saving the file.

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  • KVM-Guest does not boot: qemudParsePCIDeviceStrs

    - by markus
    I have a Server running Ubuntu 10.10 Server-Edition kvm, and libvirt (both ubuntu-native packages) HDD-Partitioning was done with LVM. Then I created some VMs with Virt-Manager and assigned LVM-Volumes to the VMs. Now the VMs do not boot. Virt-Manager shows a CPU-Usage of 100% for this Guest and the VNC-Connection states Booting from Hard Disk The VM-specific logfiles do not show any abnormality only syslog shows a warning warning : qemudParsePCIDeviceStrs:1422 : Unexpected exit status '1', qemu probably failed What can I do to find the error?

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  • 7-Zip compression on multi-core computers

    - by Peter Mortensen
    Does 7-Zip take advantage of multiprocessor or multi-core systems when compressing? For example, would there be a close to 16 times speed-up on a 16 core system assuming no disk or memory bottlenecks? Or is it is limited to 2 threads (2 times speed-up on systems with more than one CPU or core)?

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  • iotop for Linux kernel 2.6.18

    - by Lightsauce
    So it has to come to my attention that iotop isn't availalbe for 2.6.18 since it's less than 2.6.20 and requires Python 2.6+. I've done some research and came across this article: http://lserinol.blogspot.com/2009/09/io-usage-per-process-on-linux.html According to this, if these process have io stats in /proc/pid#/io (where pid# is the process #) it's doable regardless of the kernel version. So, in reality, I could upgrade Python to 2.6 and test out iotop. However, my flavor of Linux, CentOS release 5.5 (Final), only supports Python 2.4.3-44.el5 currently. If I were to do uninstall from yum, it doesn't look so pretty. It ends up wanting to uninstall 235 packages, most of which are very important! I read in one place, online (I forget the URL from yesterday), that you can install Python 2.6+ parallel to this one, and have the rpm install for iotop use that. Well, I didn't choose that route. I figured, what the heck, lets write iotop (not copying it, but reverse engineering it without actually looking at it's code/it in use) in bash. I thought it would just grab the /proc/pid#/io file and parse stats. So I wrote a script to grab the top 10 rchar, wchar, read_bytes, and write_bytes by collecting all these stats from all the /proc/pid#/io files, sorting them by each metric, then grabbing the top 10 highest values. The conclusion, the data seems completely useless. Does anybody know any resources for advanced Linux where I can figure out how to take these /proc/pid#/ directories and figure out what the heck they are doing with io on the disk? My main goal is to figure out what exactly is causing high load on my disk. I just know it's on the / partition (/dev/sda2 in this case), and I'm not really sure how to narrow it down without the help of iotop. If I run iostat to grab metrics for 1 minute, every second, the first result it gives me shows a high 'kB_read/s', so that makes me think, it's reading mostly. However, if I watch the update it gives me every second, it's actually just showing values for kB_wrtn/s. This makes me think the initial value iostat gives me is misleading.

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  • ZFS Recover from Faulted Pool State

    - by nickv2002
    I have a six disk ZFS raidz1 pool and had a recent failure requiring a disk replacement. No problem normally, but this time my server hardware died before I could do the replacement (but after and unrelated to the drive failure as far as I can tell). I was able to get another machine from a friend to rebuild the system, but in the process of moving my drives over I had to swap their cables around a bunch until I got the right configuration where the remaining 5 good disks were seen as online. This process seems to have generated some checksum errors for the pool/raidz. I have the 5 remaining drives set up now and a good drive installed and ready to take the place of the drive that died. However, since my pool state is FAULTED I'm unable to do the replacement. root@zfs:~# zpool replace tank 1298243857915644462 /dev/sdb cannot open 'tank': pool is unavailable Is there any way to recover from this error? I would think that having 5 of the 6 drives online would be enough to rebuild the right data, but that doesn't seem to be enough now. Here's the status log of my pool: root@zfs:~# zpool status tank pool: tank state: FAULTED status: One or more devices could not be used because the label is missing or invalid. There are insufficient replicas for the pool to continue functioning. action: Destroy and re-create the pool from a backup source. see: http://zfsonlinux.org/msg/ZFS-8000-5E scan: none requested config: NAME STATE READ WRITE CKSUM tank FAULTED 0 0 1 corrupted data raidz1-0 ONLINE 0 0 8 sdd ONLINE 0 0 0 sdf ONLINE 0 0 0 sdh ONLINE 0 0 0 1298243857915644462 UNAVAIL 0 0 0 was /dev/sdb1 sde ONLINE 0 0 0 sdg ONLINE 0 0 0 Update (10/31): I tried to export and re-import the array a few times over the past week and wasn't successful. First I tried: zpool import -f -R /tank -N -o readonly=on -F tank That produced this error immediately: cannot import 'tank': I/O error Destroy and re-create the pool from a backup source. I added the '-X' option to the above command to try to make it check the transaction log. I let that run for about 48 hours before giving up because it had completely locked up my machine (I was unable to log in locally or via the network). Now I'm trying a simple zpool import tank command and that seems to run for a while with no output. I'll leave it running overnight to see if it outputs anything.

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  • Using SSH, transfer webURL to remote machine

    - by AlanTuring
    Hi so i was doing some research in the library so i could use some pictures later on my Desktop computer in my room. I have space on my Lab account which i usually SSH into, and i was wondering if URL's can be directly transferred over to a remote machine and saved on the hard disk. I was thinking something like this: scp http://click.si.edu/images/truncatedurl.jpg /home3/etc.../filename.jpg is this possible? Thanks in advance.

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  • Why do my VMware Images get so large?

    - by stevebot
    Hi, I have a Centos VMware Image that I have recreated a couple times, and I notice that after a while it gets pretty large. It starts out at 8 GBs when I make it, and a week or two later it is 25GB and then a month later it is a whole 50GB or so. I am not installing anything crazy on it, and my disk usage on the VM is pretty low. Is there an option that could be affecting the size of these VMs?

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  • "Upgrading" SQL Server 2008 180-day Evaluation to Licenced Standard Edition

    - by alsan
    Hello, I run into the same issue as someone who posted this question on experts-exchange.com (couldn't read the answer though as I don't have an account there): {Quote Begin} I noticed that the 180-day Evaluation version of SQL Server 2008 is the Enterprise version. Is there going to be any problem "upgrading" the Evaluation Enterprise version to a licensed STANDARD version (and how much additional stuff is going to be left inactive on my disk and, more importantly, in my registry, etc. if I do so)? {Quote End} Any advice is appreciated.

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  • How to move the files of a replicated database (SQL Server 2008 R2) to a different drive

    - by ileon
    I would appreciate if someone could help me with the following problem: We use two SQL Server 2008 R2 databases under transactional replication: transactional publication with updatable subscriptions. because we run out of disk space we need to move the database files into a new drive. But I don't want to break the replication. What I'm looking for are the required steps that will help me to move the files to the new drive. Thanks

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  • Minimize writes to SSD disks with Windows 7

    - by mfn
    Most people use their SSD as their primary system installation disk with Windows 7. W7 already has a lot of optimizations for SSDs, both in terms of performance and lifetime. Minimizing writes increases the lifetime of SSDs, so post each suggestion as an answer and let others vote on them.

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  • MongoDB and datasets that don't fit in RAM no matter how hard you shove

    - by sysadmin1138
    This is very system dependent, but chances are near certain we'll scale past some arbitrary cliff and get into Real Trouble. I'm curious what kind of rules-of-thumb exist for a good RAM to Disk-space ratio. We're planning our next round of systems, and need to make some choices regarding RAM, SSDs, and how much of each the new nodes will get. But now for some performance details! During normal workflow of a single project-run, MongoDB is hit with a very high percentage of writes (70-80%). Once the second stage of the processing pipeline hits, it's extremely high read as it needs to deduplicate records identified in the first half of processing. This is the workflow for which "keep your working set in RAM" is made for, and we're designing around that assumption. The entire dataset is continually hit with random queries from end-user derived sources; though the frequency is irregular, the size is usually pretty small (groups of 10 documents). Since this is user-facing, the replies need to be under the "bored-now" threshold of 3 seconds. This access pattern is much less likely to be in cache, so will be very likely to incur disk hits. A secondary processing workflow is high read of previous processing runs that may be days, weeks, or even months old, and is run infrequently but still needs to be zippy. Up to 100% of the documents in the previous processing run will be accessed. No amount of cache-warming can help with this, I suspect. Finished document sizes vary widely, but the median size is about 8K. The high-read portion of the normal project processing strongly suggests the use of Replicas to help distribute the Read traffic. I have read elsewhere that a 1:10 RAM-GB to HD-GB is a good rule-of-thumb for slow disks, As we are seriously considering using much faster SSDs, I'd like to know if there is a similar rule of thumb for fast disks. I know we're using Mongo in a way where cache-everything really isn't going to fly, which is why I'm looking at ways to engineer a system that can survive such usage. The entire dataset will likely be most of a TB within half a year and keep growing.

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  • How can I transfer a user state of a win7 machine that won't boot?

    - by askvictor
    I have a windows 7 machine that won't boot completely, even in safe mode. I want to re-image the machine using a generic software image, but would like to keep the user data (including settings etc) that are on there ala Windows Easy Transfer. I can mount the hard disk on another machine - can I use Easy Transfer to transfer the user state of an account on the non-booted OS? Or do I need explore USMT?

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  • How to create a ghost environment?

    - by manwood
    I want to create a ghost or image of a fresh Windows XP development environment with all the various bits of software installed and ready to go, so that when the OS gets clogged or the main disk fails I can simply install the ghost rather than having to run through the entire install and setup process all over again. What is the best way to go about doing this? Cheers.

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  • What is the fastest method to restore MySQL replication?

    - by dwhere
    I have a MySQL (5.1) master-slave replication pair and replication to the slave has failed. It failed because the master ran out of disk space and the relay-logs became corrupt. The master is now back online and working properly. Since there is this error in the log the slave process can't simply be restarted. The server has a single 40GB InnoDB database and I would like to know what is the fastest method for getting the slave back in sync to minimize downtime.

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  • How to monitor an Amazon EC2 instance

    - by sektor
    Is there a way to monitor ec2 instances without using cloudwatch? I ask this since ec2 instances are basically VPS's, and using output from commands like top, vmstat, htop in scripts may not give the clear picture as the CPU cycles are shared between other instances as well. What should one keep in mind while monitoring CPU usage on a VPS?, should one have alerts based on top load or % of CPU used by user processes coupled with other factors like processes waiting on disk io, hardware interrupts?

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  • Installing Cygwin, what distro do I use?

    - by user2699451
    I have a fresh install of Windows and a Linux OS that I can't access, how do I fix this? I do not have the .iso/disk for Linux anymore. So I figured, I can install Cygwin and through that install Grub, but I am used to Linux Mint, which uses apt-get. I have used CentOS before which uses rpm, but how do I install and use packages in the Cygwin terminal, and is it possible to install Grub through Cygwin?

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  • Windows 7 reboot and freezing, possible power problems?

    - by mikelbring
    My Gateway LX Series desktop is about 6-8 months old. When I bought it, it had Windows Vista. I then put the RC version of Windows 7 on it. About 3 months after I bought it, it would randomly start to reboot, actually just shut off. I monitored the temperature levels and they seemed normal. So I installed a fresh Windows 7 Ultimate OEM 64bit. It actually got worse and would reboot more frequently. I then contacted Gateway and they said my machine was built for Windows Vista (made me chuckle), and told me to update my BIOS. So I did, and it was fixed for a good couple months. Recently, it started to do it again. Now I noticed early on it was doing it most often, if not every time when I was either watching a flash video or playing a flash game. So I decided to download the drivers again and I also downloaded my motherboard drivers. Seemed to be okay. A week later it started doing it again. And now it's doing it even more frequently. Sometimes I would turn it on, login into Windows and *BAM!* it would shut off. Now I am at the point where I can hardly get it to turn on. It would freeze at the point where it says "Starting Windows", with the Windows logo. Sometimes it would say "Checking disk for consistency" or whatever and freeze there (not shut off, just freeze). I even got the prompt to launch startup repair. But that also freezes when it says starting Windows. It does not really freeze, just never loads up. I am kind of lost as to what's going on. I have a few ideas but nothing I want to pursue (graphics card? hard drive?). Another thing I did try was to boot into a live disk of Ubuntu and try to launch every program I could and get on the internet but I never got it to reboot. So it sounds like to me it's a Windows thing, but I have no idea. I am just stuck and would like to see if any one has any ideas or could lead me in the right direction.

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  • Hard drive after PCB swap strange stuff

    - by ramyy
    I’ve done a PCB swap to my HDD. The HDD model is: WD6400AAKS-00A7B2. The original PCB PN matches the new one (first three letter groups), though the cache mismatches (16MB original, 8MB new). The Hardware store that made the swap told me it was hard to do the swap, they have done firmware adaptation. I can see that this firmware version does not match the original, (01.03B01 original, 05.04E05 new). Still I can see that the serial number and model of the drive is correct, the hard drive appeared normal in the BIOS, all the partitions show and everything appears normal. I have encountered three things though, I have left the drive non operated for 2-3 weeks after the swap to avoid corrupting the data or anything else the new PCB might cause, until I buy a new drive and backup the data. I got a drive, and when I powered the old drive manually (I have a laptop, I use a normal desktop power supply and a USB/SATA connector), I heard the motor start and I could hear ticking as if the motor’s somehow struggling to start, and then the motor sound starts again then the ticking, and so on.. I tried powering again it happened again. The third time it started normally and I could see everything normally. I took the chance and copied all the data over to the new drive. When I was done, I powered off the drive (after more than 25 hours of continuous operation), tried to power it up again and it did so normally, and so are the times I powered it up later; but I got very suspicious now. What could be the problem here? And what happened new, it used to power normally after the swap directly? The second thing that happened is that I found size differences with some files; some include movies, songs, (.iso) files for games, and programs. I could find the size is the same, but size on disk is a little more on the new drive for these files. . I’ve tried some of those files (with size differences) they worked fine. They are not too much but still make you suspicious of the integrity of the data copied; one cannot try if all files are working for about (580 GB) worth of data. I tried copying these files on the same partition they exist of the old drive; they are the same in size as when copied to the new drive (allocation unit size not the issue). I took an image of a partition (sector by sector including empty ones) and when I explore it, these file sizes are equal to the original (old drive); I copy them anywhere else their size on disk, increases, i.e becomes equal to the ones I copy from the old drive itself anywhere. Why the size difference and can one trust the integrity of the data?? The third thing is that when I connect my new external USB HDD, the partitions of the old HDD unmount and then mount again. Connected are: (USB mouse + Old HDD) then external HDD. Why that happens?? Considering the following: I compared the SMART reports from after the swap directly and after the copying, no error readings or reallocated sectors where reported. Here they are: http://www.image-share.com/ijpg-1939-219.html I later ran both WD data life guard tests and they came out passed. I’m worried for this drive since I must be sure the data is fine and safe on the new one, and I will consider it backup for the new one, since you can’t trust anything anymore. I hope you can forgive me for the length of the post, but couldn’t ignore any of the details, this hard drive contains very important data to me and I have to deal with the situation with great care.

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