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• Can KVM roll back changes to Virtual Disks automatically?

  - by Cygon

  I'm currently using VirtualBox on my Linux server to run a small Windows guest OS. I've configured its main virtual hard drive as what VBox calls "Immutable" - meaning that any changes to it are written into a differencing image that is discarded when the system reboots. Can KVM do something similar? I've read about snapshots via "savevm", "loadvm" but I believe that's saved states, not differencing images. What I ultimately want is a VM with two drives: one reverts on each reboot, one keeps its changes. Ideally, the unchangeable drive image should be stored with only read access granted to the user running KVM.

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• How to add addtional disks to a Windows 2008 KVM based Guest?

  - by taazaa

  I have a Win 2008 KVM based guest VM running on a Ubuntu 10 host. It is a raw image of 22G. I want to add a "data" drive which would show up as "D:\" drive on the guest. I first created a raw image using: qemu-img create -f raw ~/vmdisk2.img 50G Then, tried attaching it using virsh attach-disk. When that did not work, I tried editing the xml file of the VM directly. Both did not seem to work. I would greatly appreciate any help on how to do this and what the best practice is. I want to keep the base image small, so that I can clone it (hopefully) and then attach necessary storage based on the application at hand. Update: The xml of the vm before adding the second drive: <domain type='kvm'> <name>win08e-vm1</name> <uuid>183a4ba0-1c0b-0b04-ad01-aa7c3a4cb390</uuid> <memory>1048576</memory> <currentMemory>1048576</currentMemory> <vcpu>2</vcpu> <os> <type arch='x86_64' machine='pc-0.12'>hvm</type> <boot dev='hd'/> </os> <features> <acpi/> <apic/> <pae/> </features> <clock offset='localtime'/> <on_poweroff>destroy</on_poweroff> <on_reboot>restart</on_reboot> <on_crash>restart</on_crash> <devices> <emulator>/usr/bin/kvm</emulator> <disk type='file' device='disk'> <driver name='qemu' type='raw'/> <source file='/var/lib/libvirt/images/win08e-vm1.img'/> <target dev='hda' bus='ide'/> <address type='drive' controller='0' bus='0' unit='0'/> </disk> <disk type='file' device='cdrom'> <driver name='qemu' type='raw'/> <source file='/home/taazaa/iso/Win08ER264.iso'/> <target dev='hdc' bus='ide'/> <readonly/> <address type='drive' controller='0' bus='1' unit='0'/> </disk> <controller type='ide' index='0'> <address type='pci' domain='0x0000' bus='0x00' slot='0x01' function='0x1'/> </controller> <interface type='bridge'> <mac address='52:54:00:7f:a7:ae'/> <source bridge='br0'/> <address type='pci' domain='0x0000' bus='0x00' slot='0x03' function='0x0'/> </interface> <serial type='pty'> <target port='0'/> </serial> <console type='pty'> <target type='serial' port='0'/> </console> <input type='tablet' bus='usb'/> <input type='mouse' bus='ps2'/> <graphics type='vnc' port='-1' autoport='yes' keymap='en-us'/> <video> <model type='vga' vram='9216' heads='1'/> <address type='pci' domain='0x0000' bus='0x00' slot='0x02' function='0x0'/> </video> <memballoon model='virtio'> <address type='pci' domain='0x0000' bus='0x00' slot='0x04' function='0x0'/> </memballoon> </devices> </domain> Thanks!

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• How to know which disk has failed on a Mirrored Raid? marked as DR0 [migrated]

  - by Saariko

  Our 2ndry DC, which is on a W2K8R2 Mirrored software raid has lost it's sync, and disk management displays the failed redundancy error How do I know which of the disks has failed? (beside to try and replace one - and see if it loads and syncs) On the device manager, under disks I see both disks, one of them has an icon of: Disable, while the other doesn't Event log displays an event id 7 - bad block on Hard disk DR0 The thing is that looking in device manager, both disks are located in '0' location, which is bizzare

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• How to know which disk has failed on a Mirrored Raid? marked as DR0

  - by Saariko

  Our 2ndry DC, which is on a W2K8R2 Mirrored software raid has lost it's sync, and disk management displays the failed redundancy error How do I know which of the disks has failed? (beside to try and replace one - and see if it loads and syncs) On the device manager, under disks I see both disks, one of them has an icon of: Disable, while the other doesn't Event log displays an event id 7 - bad block on Hard disk DR0 The thing is that looking in device manager, both disks are located in '0' location, which is bizzare

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• Why doesn't Windows XP show "Total Size" and "Free Space" for USB flash disks?

  - by Mehper C. Palavuzlar

  When I double click on My Computer, I can immediately see the Total size and Free space for internal and external HDDs, and inserted CD/DVD media, but in the same columns I cannot see these values for any USB flash drives. They are just empty. To see, I have to right click on USB drive letter, and select Properties. Is there a trick to make Windows XP display USB drive's Total size and Free space in My Computer window?

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• Why is reading from my lvm mirror slower than reading from the individual disks?

  - by smoofra

  Is this really just the way lvm is, or am i doing something wrong?

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• What is the max number of devices (disks) that can be mounted?

  - by Michael Neale

  And obviously I am meaning practically - is it dozens, or hundreds?

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• How to convert WinXP + Apps on RAID0 to use just one of the two RAID disks?

  - by chris5gd

  I have two 150GB SATA drives in hardware RAID 0, on which I have my C: (Win XP) and D: (installed apps). I'm migrating to Windows 7, but I want to keep my XP system until I've got it all running smoothly. So I want to: break the RAID move C: and D: to one of the drives (there's enough room) use the other drive for Win 7 boot into one or the other Clearly I can't move C: and D: after breaking the RAID, so I'm assuming I need to image the two partitions first, then break the RAID and restore the images to one of the drives. So my questions are: Is this possible? If so, what would be a good (free) imaging/restore tool? How do I ensure that the drive will boot after restoring the images? What sort of gotchas should I look out for? If there's a better solution than this, I'd be grateful for suggestions. Thanks!

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• How can I speed up the thumbnail generation for removable disks?? Win7

  - by Saebin

  So why are my picture/video thumbnails rebuilding themselves all the time if I disconnect/reconnect a removable drive? Shouldn't these be stored on the drive or my pc?

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• Install Ubuntu 12.04 on a ACER AC100

  - by pidarn

  I'm trying to install a 12.04.1 on an ACER AC100 - Mini-Server. After booting from the Install-CD there are no Disks shown. In Bios I disabled the Intel-Raid /LSI-Raid. I want to install on the 1st of 4 "native" disks and I tried to do this with RHEL 6.4 where all Disks are visible - but the UBUNTU-Installer doesn't find any of them. btw ... If I boot from the UBUNTU - Install-CD in "rescue"-mode the disks are visible?! Any Ideas?

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• insert system disk error after switchting SATA cables

  - by Matthias

  I have 5 hard disks built in my computer, two connected by IDE cables, three by SATA. Today I had to return two of the SATA cables to my room mate. So I grabbed another one I had floating around and connected the remaining disk by unplugging my DVD R/W. Now I receive the 'insert system disk and press enter' error after booting. Disks and cables seem to be fine, since all the disks are recognized in the BIOS. Also, I can mount the disks using a live CD w/o problems. I also tried different orderings of the cables (i.e. plugging the disks in different plugs on the mainboard), I'm not sure if that even matters using SATA. Any Ideas what might be the problem here? The OS installed are Windows 7 and Ubuntu 10, the bootloader installed is GRUB. PS: No RAID involved, JBOD.

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• Disk names in Solaris 10 for ZFS: SAS WWN instead of c0t0d0

  - by notpeter

  I currently have a server running Solaris 10u9 with a SAS enclosure (Dell PowerVault MD1000) filled with SATA disks attached to an SAS card (LSI 3801E). It happily recognizes the 15 disks in the MD1000 and presents them each disk in the traditional solaris form (c1t12d0, c1t13d0, c1t15d0, etc). My home ZFS setup (Nexenta CP3 + LSI 9200-16E + directly cabled SATA disks) presents disks as their SAS WWN ID (ex: c3t600039300001EA56d0). Although this ID is longer, I've found it much easier to troubleshoot because the cabling/slot is irrelevant, ZFS just identifies the disk by ID, if it's connected it finds it. Most manufacturers print the WWN right on the disk's top label, can't get much easier than that. So how can I get Solaris to identify disks by SAS WWN instead of by the cXtXdX?

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• Wubi installation broken by update - now unable to mount

  - by Outspaced

  As of today, my wubi installation of Ubuntu won't boot (goes straight to 'minimal bash-like interface) and I am unable to mount it when I boot straight to Ubuntu. If I boot straight into Ubuntu (not using Wubi, not going via Windows), I am able to mount the Windows partition and see the Wubi partition there: sudo mount -t ntfs /dev/sda5 /media/winxp And from there I can see the wubi root disk: /media/winxp/ubuntu/disks/root.disk But if I try to mount this: sudo mount -o loop /media/winxp/ubuntu/disks/root.disk /media/wubi I get an error: /media/winxp/ubuntu/disks/root.disk Input/Output Error If I then try fsck: sudo fsck /media/winxp/ubuntu/disks/root.disk I get this: Input/Output Error while trying to open /media/winxp/ubuntu/disks/root.disk The Superblock could not be read or does not describe a correct etx2 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 want to try running e2fsk with an alternate superblock: e2fsck -b 8193 <device ... this gives me the same result. There is data on this partition that I really need to be able to access, so I can't delete and reinstall. Any help much appreciated. Thanks.

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• How many disk should I use to meed the capacity and IOPS need?

  - by facebook-100005613813158

  An application needs 1.6 TB of storage capacity and performs 1000 IOPS. How many disks are required to meet the application requirement and offer acceptable response time? The disk specifications are as follows: - Drive capacity = 100 GB - 15K RPM - Each disk can perform 50 IOPS 4 candidate , 10,12,16,20, which one is the most likely answer? in my opinion,16 disks can only meet the capacity need ,but cannot meet the IOPS need, so ,the right answer should be 20 disks?right?

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• Avoid random disk names

  - by BarsMonster

  Hi! I have Ubuntu Server 10.04 1 system disk, and 5 disks in RAID-5 configuration. The problem is that names of these disks are changed from time to time, they are being randomly mixed from time to time (sda,b,c,d,e,f - so system disks might be sda, or sdc at different time for example).... is there any way to fix drive names, so that even if it's disconnected for example, no other drive can occupy this letter based on disk UUID or something?

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• Hyper-V R2: Need help with disk structure

  - by MojoDK

  Hi all, I'm going to use the free (non gui) version of Hyper-V R2. In my new server I have 8 disks in total (for Hyper-V R2 installation and virtual machine). Atm I'm going to run a single virtual machine, with following tasks: Windows Server 2008 R2 x64 File/Print SQL Server My question is ... with my 8 disks in the server, which disks should contain wich data? Should I install "Hyper-V R2" and VM's drive c on same physical disks? Should I use raid 1 or 5? With the above tasks, how would you structure the disks? Hope you know what I mean (I'm not english, so it's difficult to explain). Thanks!!! Mojo

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• Generalized strategy for file server virtualization in Xenserver

  - by Jamie

  I'm not shopping as much as I'm looking for some guidance on good idea / bad idea strategies. I'm sure I'm not in the "best practices" budget range. Currently, I have 3 dell poweredges running xenserver in a pool. Each node has a ubuntu file server, serving about 6TB. One is the primary, the other two are rsync targets for backup. The 6TB is stored on their respective local storage disks as an LVM of 3x2tb virtual disks. The fileserver VM disks are also stored on the node local disks. Each node also runs a smattering of light-weight VMs for web, development, windows VMs, and stuff like that. Several of those VM's disks reside on a QNAP NAS to play with live migration. These VM's are often clients of the primary file server (like all the mail, web content, user files are stored on the file server, not on the mail, web, and samba VMs). This all works fine, and is a major step up for us. The downside is that the QNAP is a single point of failure. And the only thing the QNAP is doing is serving migratable VM images, not client data. Someday the poweredge local arrays will be full, and we will have to reinvent ourselves again. Is it wise to have heavywieght vms (like the fileserver, with its 6+ TB disks) on a SAN or NAS? Would it be better to keep the VMs lightweight, have the VM images on a SAN or NAS, and use 2 or more NAS act as NFS-serving file appliances? A hybrid SAN/NAS that can serve iscsi for images and NFS for the client vms? It seems like live-magration would be a misnomer if you have to migrate a fileserver with its entire 6+ TB disk. I recognize there are plenty of ways to skin the cat. We've already skinned it a few ways. What makes sense?

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• LSI1068E hidden drives after failed raid volume creation

  - by silk

  We are using LSI 1068E raid chipset with SAS drives. We had added new drives to the system, and tried to create new raid volume with the lsiutil, unfortunately the creation failed. The problem is that now we do not have the new raid volume and disks 'disappeared' and are not available as targets for raid. Lsiutil option 8 (scan for devices) does not display these disks at all. lsiutil option 16 (display attached devices) does list them as targets. lsiutil option 21+30 (create raid) does not list these disks. Just after insrting them to enclosure these disks appeared in the system, as expected. During the raid creation kernel logged: Mar 4 08:40:02 kilo kernel: [57555.687946] mptbase: ioc0: RAID STATUS CHANGE for PhysDisk 2 id=0 Mar 4 08:40:02 kilo kernel: [57555.687978] mptbase: ioc0: PhysDisk has been created Mar 4 08:40:02 kilo kernel: [57555.695438] scsi target0:0:2: mptsas: ioc0: RAID Hidding: fw_channel=0, fw_id=0, physdsk 2, sas_addr 0x5000c50008ebe5fd for both of them, again as expected. Unfortunately they did not appear back even though the volume was not created. The same situation is in the controller's bios after a reboot. Taking the disks out and inserting in different slots did not help, either. Has someone seen a similar problem? And knows how to 'get back' our disks?

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• Swapping RAID sets in and out of the same controller

  - by hazymat

  This is a really simple question, and the answer is probably encoded in various wikipedia articles, however my question is reasonably specific, and I need a bulletproof answer! I'm not sure if my question pertains to hardware RAID in general, or to the specific RAID controller I'm working on. Either way it is the Dell SAS 6/iR (this is an LSI sas1068e chipset). I simply want to: remove a set of striped (RAID 0) disks from this RAID controller in a server put in another set of disks, and create a RAID 1 array (or create a new 'virtual disk', as they call it in the SAS 6/iR manual) Do stuff with the new RAID 1 array Have the option of putting back the old set of disks (the RAID 0 striped ones) I am quite sure this is possible, but I need some form of reliable, evidence-based answer as it's for a client of mine, and I need to migrate their data safely. The question: can I actually do the above? Does the RAID configuration get stored on the disks themselves, or in the hardware controller? Is any data stored in the hardware controller? If there is any chance I cannot completely restore operation of the first set of disks I removed, then I need to know about it! The manual alludes to the answer to this question (see page 45 of this document), and talks about activating an array of disks. I just need someone to confirm I can definitely do the above. See, simple question, right? :)

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• Bad disk performance on HP DL360 with Smarty Array P400i RAID controller

  - by sarge

  I have a HP DL360 server with 4x 146GB SAS disks and a Smart Array P400i RAID controller with 256MB cache. The disks are in RAID 5 (3 disks + 1 hot spare). The server is running VMware ESX 3i. The disk write performance is really bad. Here are some numbers: ns1:~# hdparm -tT /dev/sda /dev/sda: Timing cached reads: 3364 MB in 2.00 seconds = 1685.69 MB/sec Timing buffered disk reads: 18 MB in 3.79 seconds = 4.75 MB/sec ns1:~# time sh -c "dd if=/dev/zero of=ddfile bs=8k count=125000 && sync" 125000+0 records in 125000+0 records out 1024000000 bytes (1.0 GB) copied, 282.307 s, 3.6 MB/s real 4m52.003s user 0m2.160s sys 3m10.796s Compared to another server those number are terrible: Dell R200, 2x 500GB SATA disks, PERC raid controller (disks are mirrored). web4:~# hdparm -tT /dev/sda /dev/sda: Timing cached reads: 6584 MB in 2.00 seconds = 3297.79 MB/sec Timing buffered disk reads: 316 MB in 3.02 seconds = 104.79 MB/sec web4:~# time sh -c "dd if=/dev/zero of=ddfile bs=8k count=125000 && sync" 125000+0 records in 125000+0 records out 1024000000 bytes (1.0 GB) copied, 35.2919 s, 29.0 MB/s real 0m36.570s user 0m0.476s sys 0m32.298s The server isn't very loaded and the VMware Infrastructure Client performance monitor is showing 550KBps average read and 1208KBps average write for the last 30 minutes (highest write rate: 6.6MBps). This has been a problem from the start. Any ideas?

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• mdadm superblock hiding/shadowing partition

  - by Kjell Andreassen

  Short version: Is it safe to do mdadm --zero-superblock /dev/sdd on a disk with a partition (dev/sdd1), filesystem and data? Will the partition be mountable and the data still there? Longer version: I used to have a raid6 array but decided to dismantle it. The disks from the array are now used as non-raid disks. The superblocks were cleared: sudo mdadm --zero-superblock /dev/sdd The disks were repartitioned with fdisk and filesystems created with mfks.ext4. All disks where mounted and everything worked fine. Today, a couple of weeks later, one of the disks is failing to be recognized when trying to mount it, or rather the single partition on it. sudo mount /dev/sdd1 /mnt/tmp mount: special device /dev/sdd1 does not exist fdisk claims there to be a partition on it: sudo fdisk -l /dev/sdd Disk /dev/sdd: 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: 0xb06f6341 Device Boot Start End Blocks Id System /dev/sdd1 1 243201 1953512001 83 Linux Of course mount is right, the device /dev/sdd1 is not there, I'm guessing udev did not create it because of the mdadm data still on it: sudo mdadm --examine /dev/sdd /dev/sdd: Magic : a92b4efc Version : 1.2 Feature Map : 0x0 Array UUID : b164e513:c0584be1:3cc53326:48691084 Name : pringle:0 (local to host pringle) Creation Time : Sat Jun 16 21:37:14 2012 Raid Level : raid6 Raid Devices : 6 Avail Dev Size : 3907027120 (1863.02 GiB 2000.40 GB) Array Size : 15628107776 (7452.06 GiB 8001.59 GB) Used Dev Size : 3907026944 (1863.02 GiB 2000.40 GB) Data Offset : 2048 sectors Super Offset : 8 sectors State : clean Device UUID : 3ccaeb5b:843531e4:87bf1224:382c16e2 Update Time : Sun Aug 12 22:20:39 2012 Checksum : 4c329db0 - correct Events : 1238535 Layout : left-symmetric Chunk Size : 512K Device Role : Active device 3 Array State : AA.AAA ('A' == active, '.' == missing) My mdadm --zero-superblock apparently didn't work. Can I safely try it again without losing data? If not, are there any suggestion on what do to? Not starting mdadm at all on boot might be a (somewhat unsatisfactory) solution.

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• Dell PE2950 - slow IO rates for writing and reading locally

  - by OrenM

  I'm having a serious issue with dell server PE2950. The server has really slow IO rates, so slow that I'm not able to use it anymore I tried few things to solve this: changing disks to new disks (configured them as raid1) changing perc card + perc cables reinstalling the OS of course, had to cause of changing of disks, centos 5.5 x64bit firmware update to everything virtual disks policy: No Read Ahead,Write Back, disk cache policy disabled. openmanage doesn't alert about anything, also i ran dell's diag tests, everything passed, also dell didn't see anything in deset log. dell offered to reseat everything, including the cpu, we did that as well, still io rates are slow I have several PE2950 servers, and I never had such a thing with any of those. All have similar or exact hardware as this one, all configured the same, with the same os centos 5.5 x64, same disks, same raid, same policy. Just for comparison: the problematic PE2950 server: [root@bad ~]# time sh -c "dd if=/dev/zero of=/tmp/ddfile bs=8k count=200000 && sync" 200000+0 records in 200000+0 records out 1638400000 bytes (1.6 GB) copied, 27.7946 seconds, 58.9 MB/s real 0m33.968s user 0m0.531s sys 0m26.000s good PE2950 server (with the exact same hardware): [root@good ~]# time sh -c "dd if=/dev/zero of=/tmp/ddfile bs=8k count=200000 && sync" 200000+0 records in 200000+0 records out 1638400000 bytes (1.6 GB) copied, 3.19999 seconds, 512 MB/s real 0m7.694s user 0m0.053s sys 0m4.057s Hopefully you will have an idea what can cause the problem.

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• Does Hyper-V support SCSI Pass-through discs in a Server 2003 R2 VM?

  - by Peter Bernier

  I'm running into some difficulties getting pass-through disks to be accessible to a Hyper-v server 2003 r2 virtual machine. Host OS : Server 2008 R2 full w/Hyper-V role Guest OS : Server 2003 R2 (Windows Home Server) The guest's OS disk is a pass-through disk on the IDE controller (not the best solution, but I can live with it). My storage disks will be pass-through disks on the SCSI controller. I'm able to see all of the disks that I'll be using for the VM on the host without issue. The problem that I'm having is that I can't seem to get the guest OS to be able to 'see' the storage drives (as pass-through disks on the SCSI controller). Here's what I'm doing : On the host, the storage drive is set to 'Offline' just like the OS disk (this is required for pass-through to work). In the VM, the storage drive is on the SCSI controller. Hyper-V Integration Tools are installed in guest. That's as far as I'm able to get. I don't see the drive in Computer Management, or in Windows Explorer (I've tried with an unformatted disk, as well as after formatting a partition). I am able to see a removable device that lists the disk's model number in the Guest, but I can't seem to access the storage. (I get an entry in Device Manager that needs drivers, but nothing on the Integration Tools disc works..) Trouble-shooting steps I've tried : If put the pass-through drive on the IDE controller, I can see it in the Guest. If put the storage drive 'Online' in the host and create a VHD on it on the SCSI controller, I can see it in the Guest. I suppose I could create a fixed-size VHD that consumes the entire disk, but I'd rather not have that overhead. I've also extracted the contents of the Integration Tools drivers (x86 and amd64) and tried pointing the disk controller to each of those, with no luck. Can anyone offer suggestions as to how I can get this to work properly?

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• Can someone explain RAID-0 in plain English?

  - by Edward Tanguay

  I've heard about and read about RAID throughout the years and understand it theoretically as a way to help e.g. server PCs reduce the chance of data loss, but now I am buying a new PC which I want to be as fast as possible and have learned that having two drives can considerably increase the perceived performance of your machine. In the question Recommendations for hard drive performance boost, the author says he is going to RAID-0 two 7200 RPM drives together. What does this mean in practical terms for me with Windows 7 installed, e.g. can I buy two drives, go into the device manager and "raid-0 them together"? I am not a network administrator or a hardware guy, I'm just a developer who is going to have a computer store build me a super fast machine next week. I can read the wikipedia page on RAID but it is just way too many trees and not enough forest to help me build a faster PC: RAID-0: "Striped set without parity" or "Striping". Provides improved performance and additional storage but no redundancy or fault tolerance. Because there is no redundancy, this level is not actually a Redundant Array of Inexpensive Disks, i.e. not true RAID. However, because of the similarities to RAID (especially the need for a controller to distribute data across multiple disks), simple strip sets are normally referred to as RAID 0. Any disk failure destroys the array, which has greater consequences with more disks in the array (at a minimum, catastrophic data loss is twice as severe compared to single drives without RAID). A single disk failure destroys the entire array because when data is written to a RAID 0 drive, the data is broken into fragments. The number of fragments is dictated by the number of disks in the array. The fragments are written to their respective disks simultaneously on the same sector. This allows smaller sections of the entire chunk of data to be read off the drive in parallel, increasing bandwidth. RAID 0 does not implement error checking so any error is unrecoverable. More disks in the array means higher bandwidth, but greater risk of data loss. So in plain English, how can "RAID-0" help me build a faster Windows-7 PC that I am going to order next week?

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• Very poor read performance compared to write performance on md(raid1) / crypt(luks) / lvm

  - by Android5360

  I'm experiencing very poor read performance over raid1/crypt/lvm. In the same time, write speeds are about 2x+ faster on the same setup. On another raid1 setup on the same machine I get normal read speeds (maybe because I'm not using cryptsetup). OS related disks: sda + sdb. I have raid1 configuration with two disks, both are in place. I'm using LVM over the RAID. No encryption. Both disks are WD Green, 5400 rpm. IO test results on this raid1: dd if=/dev/zero of=/tmp/output.img3 bs=8k count=256k conv=fsync - 2147483648 bytes (2.1 GB) copied, 22.3392 s, 96.1 MB/s sync echo 3 > /proc/sys/vm/drop_caches dd if=/tmp/output.img3 of=/dev/null bs=8k - 2147483648 bytes (2.1 GB) copied, 15.9 s, 135 MB/s And here is the problematic setup (on the same machine). Currently I have only one sdc (WD Green, 5400rpm) configured in software raid1 + crypt (luks, serpent-xts-plain) + lvm. Tomorrow I will attach another disk (sdd) to complete this two-disk raid1 setup. IO tests results on this raid1: dd if=/dev/zero of=output.img3 bs=8k count=256k conv=fsync 2147483648 bytes (2.1 GB) copied, 17.7235 s, 121 MB/s sync echo 3 > /proc/sys/vm/drop_caches dd if=output.img3 of=/dev/null bs=8k 2147483648 bytes (2.1 GB) copied, 36.2454 s, 59.2 MB/s We can see that the read performance is very very bad (59MB/s compared to 135MB/s when using no encryption). Nothing is using the disks during benchmark. I can confirm this because I checked with iostat and dstat. Details on the hardware: disks: all are WD green, 5400rpm, 64mb cache. cpu: FX-8350 at stock speed ram: 4x4GB at 1066Mhz. Details on the software: OS: Debian Wheezy 7, amd64 mdadm: v3.2.5 - 18th May 2012 LVM version: 2.02.95(2) (2012-03-06) LVM Library version: 1.02.74 (2012-03-06) LVM Driver version: 4.22.0 cryptsetup: 1.4.3 Here is how I configured the slow raid1+crypt+lvm setup: parted /dev/sdc mklabel gpt type: ext4 start: 2048s end: -1 Now the raid, crypt and the lvm configuration: mdadm --create /dev/md1 --level=1 --raid-disks=2 missing /dev/sdc cryptsetup --cipher serpent-xts-plain luksFormat /dev/md1 cryptsetup luksOpen /dev/md1 md1_crypt vgcreate vg_sql /dev/mapper/md1_crypt lvcreate -l 100%VG vg_sql -n lv_sql mkfs.ext4 /dev/mapper/vg_sql-lv-sql mount /dev/mapper/vg_sql-lv_sql /sql So guys, can you help me identify the reason and fix it? It has to be something with the cryptsetup as there is no such read slowdown on the other setup (sda+sdb) where no encryption is present. But I have no idea what to do. Thanks!

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