https://wiki.archlinux.org/api.php?action=feedcontributions&user=Fabertawe&feedformat=atomArchWiki - User contributions [en]2024-03-29T12:04:03ZUser contributionsMediaWiki 1.41.0https://wiki.archlinux.org/index.php?title=RAID&diff=229206RAID2012-10-17T10:36:54Z<p>Fabertawe: /* Removing device, stop using the array */</p>
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<div>[[Category:Getting and installing Arch]]<br />
[[Category:File systems]]<br />
[[it:RAID]]<br />
{{Article summary start}}<br />
{{Article summary text|This article explains what RAID is and how to install, configure and maintain it.}}<br />
{{Article summary heading|Required software}}<br />
{{Article summary link|mdadm|http://neil.brown.name/blog/mdadm}}<br />
{{Article summary link|parted|http://www.gnu.org/software/parted/}}<br />
{{Article summary heading|Related}}<br />
{{Article summary wiki|Software RAID and LVM}}<br />
{{Article summary wiki|Installing with Fake RAID}}<br />
{{Article summary wiki|Convert a single drive system to RAID}}<br />
{{Article summary end}}<br />
<br />
== Introduction ==<br />
{{Wikipedia|RAID}}<br />
Redundant Array of Independent Disks (RAID) devices are virtual devices created from two or more real block devices. This allows multiple devices (typically disk drives or partitions thereof) to be combined into a single device to hold (for example) a single filesystem. RAID is designed to prevent data loss in the event of a hard disk failure. There are different [[Wikipedia:Standard RAID levels|levels of RAID]].<br />
<br />
===Standard RAID levels===<br />
; [[Wikipedia:Standard RAID levels#RAID 0|RAID 0]]: Uses striping to combine disks. Not really RAID in that it ''provides no redundancy''. It does, however, ''provide a big speed benefit''. This example will utilize RAID 0 for swap, on the assumption that a desktop system is being used, where the speed increase is worth the possibility of system crash if one of your drives fails. On a server, a RAID 1 or RAID 5 array is more appropriate. The size of a RAID 0 array block device is the size of the smallest component partition times the number of component partitions.<br />
; [[Wikipedia:Standard RAID levels#RAID 1|RAID 1]]: The most straightforward RAID level: straight mirroring. As with other RAID levels, it only makes sense if the partitions are on different physical disk drives. If one of those drives fails, the block device provided by the RAID array will continue to function as normal. The example will be using RAID 1 for everything except swap. Note that RAID 1 is the only option for the boot partition, because bootloaders (which read the boot partition) do not understand RAID, but a RAID 1 component partition can be read as a normal partition. The size of a RAID 1 array block device is the size of the smallest component partition.<br />
; [[Wikipedia:Standard RAID levels#RAID 5|RAID 5]]: Requires 3 or more physical drives, and provides the redundancy of RAID 1 combined with the speed and size benefits of RAID 0. RAID 5 uses striping, like RAID 0, but also stores parity blocks distributed across each member disk. In the event of a failed disk, these parity blocks are used to reconstruct the data on a replacement disk. RAID 5 can withstand the loss of one member disk.<br />
: {{Note|RAID 5 is a common choice due to its combination of speed and data redundancy. The caveat is that if 1 drive were to fail and before that drive was replaced another drive failed, all data will be lost. For excellent information regarding this, see the ''[http://ubuntuforums.org/showthread.php?t&#x3d;1588106 RAID5 Risks]'' discussion thread on the Ubuntu forums. The best alternative to RAID5 when redundancy is crucial is RAID 10.}}<br />
<br />
===Nested RAID levels===<br />
; [[Wikipedia:Nested RAID levels#RAID 1 + 0|RAID 1+0]]: Commonly referred to as ''RAID 10'', is a nested RAID that combines two of the standard levels of RAID to gain performance and additional redundancy.<br />
<br />
=== Redundancy ===<br />
{{Warning|Installing a system with RAID is a complex process that may destroy data. Be sure to backup all data before proceeding.}}<br />
<br />
RAID does not provide a guarantee that your data is safe. If there is a fire, if your computer is stolen or if you have multiple hard drive failures, RAID will not protect your data. Therefore it is important to make backups (see [[Backup Programs]]). Whether you use tape drives, DVDs, CDROMs or another computer, keep an current copy of your data out of your computer (and preferably offsite). Get into the habit of making regular backups. You can also divide the data on your computer into current and archived directories. Then back up the current data frequently, and the archived data occasionally.<br />
<br />
=== RAID level comparison ===<br />
{| class="wikitable" border="1" cellpadding="5" cellspacing="0"<br />
! RAID level!!Data redundancy!!Physical drive utilization!!Read performance!!Write performance!!Min drives<br />
|-<br />
| '''0'''||'''No'''||100%||'''Superior'''||'''Superior'''||1<br />
|-<br />
| '''1'''||Yes||50%||Very high||Very high||2<br />
|-<br />
| '''5'''||Yes||67% - 94%||'''Superior'''||High||3<br />
|-<br />
| '''6'''||Yes||50% - 88%||Very High||High||4<br />
|-<br />
| '''10'''||Yes||50%||Very high||Very high||4<br />
|}<br />
<br />
==Installation==<br />
[[pacman|Install]] {{Pkg|mdadm}} and {{Pkg|parted}}, available in the [[Official Repositories]].<br />
<br />
===Prepare the device===<br />
To prevent possible issues down the line, you should consider wiping your entire disk before setting up RAID. This should be repeated for each disk you will be using for RAID, these commands completely erase anything currently on the device!<br />
{{Warning|These steps erase everything on the {{ic|/dev/disk-to-clean}} so type carefully}}<br />
<br />
Erase any old RAID configuration info<br />
{{bc|1=# mdadm --zero-superblock /dev/disk-to-clean}}<br />
<br />
Erase all partition-table data<br />
{{bc|1=# dd if=/dev/zero of=/dev/disk-to-clean bs=4096 count=1}}<br />
<br />
Make sure kernel clears old entries<br />
{{bc|1=# partprobe -s}}<br />
<br />
Verify the entries in {{ic|/etc/fstab}} and {{ic|/etc/mdadm.conf}}<br />
<br />
With a software RAID, disabling the hard disk cache will help prevent data loss during power loss, as long as you do not use a [[Wikipedia:Uninterruptible power supply|UPS]]. Repeat the command for each drive in the array. Note however, that this decreases performance.<br />
{{bc|# hdparm -W 0 /dev/path_to_disk}}<br />
<br />
===Create the partition table===<br />
The RAID setup varies between different RAID-levels. If you know what RAID you want and already set up your hardware accordingly, you can proceed with formatting the disks you want in your array. It is also possible to create a RAID-array directly on the raw disks (without partitions), but not recommended because it can cause problems when swapping a failed disk.<br />
<br />
When replacing a failed disk of a RAID-array, the new disk has to be exactly the same size as the failed disk or bigger — otherwise the array recreation process will not work. Even hard drives of the same manufacturer and model can have small size differences. By leaving a little space at the end of the disk unallocated one can compensate for the size differences between drives, which makes choosing a replacement drive model easier. Therefore, it is good practice to leave about 100 MB of unallocated space at the end of the disk. <br />
<br />
Format one of the drives in the array with your favorite tool. For example,<br />
{{bc|# cfdisk /dev/path_to_disk}}<br />
{{Tip|Using GParted to create the partitions and align them to the cylinder will create optimized disk alignment. This can be achieved using the [http://gparted.sourceforge.net/livecd.php Gnome Partition Editor Live Media].}}<br />
<br />
====Partition code====<br />
The two [[Wikipedia:Partition types|partition type]]s that are applicable to RAID devices are Non-FS data and Linux RAID auto. Non-FS data is recommended, as your array is not auto-assembled during boot. With Linux RAID auto one may run into trouble when booting from a live-cd or when installing the degraded RAID-array in a different system (maybe with other degraded RAID-arrays in worst case) as Linux will try to automatically assemble and resync the array which could render your data on the array unreadable if it fails.<br />
<br />
{{note|cfdisk and mkpart use a set of "filesystem types" to set the partition codes. Each type corresponds to a partition code (see [http://www.gnu.org/software/parted/manual/html_node/mkpart.html#mkpart Parted User's Manual]). It uses the {{ic|da}} type to denote Non-FS data and {{ic|fd}} for Linux RAID auto.}}<br />
<br />
===Copy the partition table===<br />
Once you have a properly partitioned and aligned disk you can copy the setup to any other disk.<br />
<br />
Verify your partitions meet basic requirements:<br />
{{bc|1=# sfdisk -lRV /dev/path_to_formatted_array_disk}}<br />
<br />
Dump the partition table from the formatted disk to a file:<br />
{{bc|<nowiki># sfdisk -d /dev/path_to_formatted_array_disk > ~/formatted_array.dump</nowiki>}}<br />
<br />
Copy the partition table from the disk dump file to all other disks in the array: <br />
{{bc|<nowiki># sfdisk /dev/path_to_unformatted_array_disk < ~/formatted_array.dump</nowiki>}}<br />
<br />
After repeating the command for every unformatted disk of the array, verify that the disks are identical with<br />
# fdisk -l<br />
or<br />
# sfdisk -l -u S<br />
<br />
===Build the array===<br />
Now build the array (e.g. [http://fomori.org/blog/blog/2011/10/19/raid5-server-to-hold-all-your-data-%e2%80%94-the-nas-alternative/ post on RAID5 setup]).<br />
<br />
{{Warning|Make sure to change the '''bold values''' below to match your setup.}}<br />
<br />
{{bc| <nowiki># mdadm --create --verbose /dev/md/your_array --level=</nowiki>'''5''' <nowiki>--metadata=</nowiki>'''1.2''' <nowiki>--chunk=</nowiki>'''256''' <nowiki>--raid-devices=</nowiki>'''5 /dev/path_to_array_disk-1 /dev/path_to_array_disk-2 /dev/path_to_array_disk-3 /dev/path_to_array_disk-4 /dev/path_to_array_disk-5''' }}<br />
<br />
The array is created under the virtual device {{ic|/dev/md/your_array}}, assembled and ready to use (in degraded mode). You can directly start using it while mdadm resyncs the array in the background. It can take a long time to restore parity, you can check the progress with:<br />
<br />
{{bc|$ cat /proc/mdstat}}<br />
<br />
===Update configuration file===<br />
Since the installer builds the initrd using {{ic|/etc/mdadm.conf}} in the target system, you should update the default configuration file. The default file can be overwritten using the redirection operator, because it only contains explanatory comments.<br />
<br />
Redirect the contents of the metadata stored on the named devices to the configuration file:<br />
# mdadm --examine --scan > /etc/mdadm.conf<br />
<br />
{{Note|If you are updating your RAID configuration from within the Arch Installer by swapping to another TTY, you will need to ensure that you are writing to the correct {{ic|mdadm.conf}} file:}}<br />
# mdadm --examine --scan > /mnt/etc/mdadm.conf<br />
<br />
Once the configuration file has been updated the array can be assembled using mdadm:<br />
# mdadm --assemble --scan<br />
<br />
===Configure filesystem===<br />
The array can now be formatted like any other disk, just keep in mind that:<br />
* Due to the large volume size not all filesystems are suited (see: [[Wikipedia:Comparison of file systems#Limits|File system limits]]).<br />
* The filesystem should support growing and shrinking while online (see: [[Wikipedia:Comparison of file systems#Features|File system features]]).<br />
* The biggest performance gain you can achieve on a raid array is to make sure you format the volume aligned to your RAID stripe size (see: [http://wiki.centos.org/HowTos/Disk_Optimization RAID Math]).<br />
<br />
===Assemble array on boot===<br />
If you selected the Non-FS data partition code the array will not be automatically recreated after the next boot. To assemble the array issue the following command:<br />
{{bc| <nowiki># mdadm --assemble --scan /dev/your_array --uuid=your_array_uuid</nowiki> }}<br />
<br />
or write it to {{ic|rc.local}}.<br />
<br />
<br />
===Add to kernel image===<br />
See [[mkinitcpio]] for more info.<br />
<br />
Add '''mdadm''' or '''mdadm_udev''' to the ''HOOKS='' section of the {{ic|/etc/mkinitcpio.conf}} file before the filesystems hook. This will add support for mdadm directly into the init image.<br />
{{bc|1= HOOKS="base udev autodetect pata scsi sata '''mdadm_udev''' filesystems usbinput fsck"}}<br />
<br />
You can view available hooks for the ''HOOKS='' section with: {{bc|1=# mkinitcpio -L}} and find out information about each hook with: {{bc|1=# mkinitcpio -H mdadm_udev}}<br />
<br />
Add '''raid456''' module and the filesystem module used on the raid (ext4) to the ''MODULES='' section of the {{ic|/etc/mkinitcpio.conf}} file. This will build these modules into the kernel image.<br />
{{bc|1= MODULES="'''ext4 raid456'''"}}<br />
<br />
Next regenerate your initrd and kernel image with: {{bc|1=# pacman -Sf linux}}<br />
<br />
== Mounting from a Live CD ==<br />
<br />
If you want to mount your RAID partition from a Live CD, use<br />
# mdadm --assemble /dev/md0 /dev/sda3 /dev/sdb3 /dev/sdc3<br />
<br />
(or whatever mdX and drives apply to you)<br />
<br />
{{Note | Live CDs like [http://www.sysresccd.org/Main_Page SystemrescueCD] assemble the RAID arrays automatically at boot time if you used the partition type fd at the install of the array)}}<br />
<br />
==Removing device, stop using the array==<br />
<br />
You can remove a device from the array after you mark it as faulty.<br />
<br />
# mdadm --fail /dev/md0 /dev/sdxx<br />
<br />
Then you can remove it from the array.<br />
<br />
# mdadm -r /dev/md0 /dev/sdxx<br />
<br />
Remove device permanently (for example in the case you want to use it individally from now on).<br />
Issue the two commands described above then:<br />
<br />
# mdadm --zero-superblock /dev/sdxx<br />
<br />
After this you can use the disk as you did before creating the array.<br />
<br />
{{Warning | If you reuse the removed disk without zeroing the superblock you will '''LOSE''' all your data next boot. (After mdadm will try to use it as the part of the raid array). '''DO NOT''' issue this command on linear or RAID0 arrays or you will '''LOSE''' all your data on the raid array. }}<br />
<br />
Stop using an array:<br />
# Umount target array<br />
# Stop the array with: {{ic|mdadm --stop /dev/md0}}<br />
# Repeat the three command described in the beginning of this section on each device.<br />
# Remove the corresponding line from /etc/mdadm.conf<br />
<br />
== Adding a device to the array ==<br />
Adding new devices with mdadm can be done on a running system with the devices mounted.<br />
Partition the new device {{ic|/dev/sdx}} using the same layout as one of those already in the arrays {{ic|/dev/sda}}.<br />
# sfdisk -d /dev/sda > table<br />
# sfdisk /dev/sdx < table<br />
<br />
Assemble the RAID arrays if they are not already assembled:<br />
# mdadm --assemble /dev/md1 /dev/sda1 /dev/sdb1 /dev/sdc1<br />
# mdadm --assemble /dev/md2 /dev/sda2 /dev/sdb2 /dev/sdc2<br />
# mdadm --assemble /dev/md0 /dev/sda3 /dev/sdb3 /dev/sdc3<br />
<br />
First, add the new device as a Spare Device to all of the arrays. We will assume you have followed the guide and use separate arrays for {{ic|/boot}} RAID 1 (/dev/md1), {{ic|swap}} RAID 1 (/dev/md2) and {{ic|root}} RAID 5 (/dev/md0).<br />
# mdadm --add /dev/md1 /dev/sdx1<br />
# mdadm --add /dev/md2 /dev/sdx2<br />
# mdadm --add /dev/md0 /dev/sdx3<br />
<br />
This should not take long for mdadm to do. Check the progress with:<br />
# cat /proc/mdstat<br />
<br />
Check that the device has been added with the command:<br />
# mdadm --misc --detail /dev/md0<br />
<br />
It should be listed as a Spare Device.<br />
<br />
Tell mdadm to grow the arrays from 3 devices to 4 (or however many devices you want to use):<br />
# mdadm --grow -n 4 /dev/md1<br />
# mdadm --grow -n 4 /dev/md2<br />
# mdadm --grow -n 4 /dev/md0<br />
<br />
This will probably take several hours. You need to wait for it to finish before you can continue. Check the progress in {{ic|/proc/mdstat}}. The RAID 1 arrays should automatically sync {{ic|/boot}} and {{ic|swap}} but you need to install Grub on the MBR of the new device manually. [[Installing_with_Software_RAID_or_LVM#Install_Grub_on_the_Alternate_Boot_Drives]]<br />
<br />
The rest of this guide will explain how to resize the underlying LVM and filesystem on the RAID 5 array.<br />
{{Note|I am not sure if this can be done with the volumes mounted and will assume you are booting from a live-cd/usb}}<br />
<br />
If you are have encrypted your LVM volumes with LUKS, you need resize the LUKS volume first. Otherwise, ignore this step.<br />
# cryptsetup luksOpen /dev/md0 cryptedlvm<br />
# cryptsetup resize cryptedlvm<br />
<br />
Activate the LVM volume groups:<br />
# vgscan<br />
# vgchange -ay<br />
<br />
Resize the LVM Physical Volume {{ic|/dev/md0}} (or e.g. {{ic|/dev/mapper/cryptedlvm}} if using LUKS) to take up all the available space on the array. You can list them with the command "pvdisplay".<br />
# pvresize /dev/md0<br />
<br />
Resize the Logical Volume you wish to allocate the new space to. You can list them with "lvdisplay". Assuming you want to put it all to your {{ic|/home}} volume:<br />
# lvresize -l +100%FREE /dev/array/home<br />
<br />
To resize the filesystem to allocate the new space use the appropriate tool. If using ext2 you can resize a mounted filesystem with ext2online. For ext3 you can use resize2fs or ext2resize but not while mounted.<br />
<br />
You should check the filesystem before resizing.<br />
# e2fsck -f /dev/array/home<br />
# resize2fs /dev/array/home<br />
<br />
Read the manuals for lvresize and resize2fs if you want to customize the sizes for the volumes.<br />
<br />
== Monitoring ==<br />
A simple one-liner that prints out the status of your Raid devices:<br />
{{hc|awk '/^md/ {printf "%s: ", $1}; /blocks/ {print $NF}' </proc/mdstat<br />
|md1: [UU]<br />
md0: [UU]<br />
}}<br />
<br />
===Watch mdstat===<br />
{{bc|watch -t 'cat /proc/mdstat'}}<br />
Or preferably using {{pkg|tmux}}<br />
{{bc|tmux split-window -l 12 "watch -t 'cat /proc/mdstat'"}}<br />
<br />
===Track IO with iotop===<br />
The {{pkg|iotop}} package lets you view the input/output stats for processes. Use this command to view the IO for raid threads.<br />
<br />
{{bc|<nowiki>iotop -a -p $(sed 's, , -p ,g' <<<`pgrep "_raid|_resync|jbd2"`)</nowiki>}}<br />
<br />
===Mailing on events===<br />
You need a smtp mail server (sendmail) or at least an email forwarder (ssmtp/msmtp). Be sure you have configured an email in {{ic|/etc/mdadm.conf}}<br />
<br />
# mdadm --monitor --scan --test<br />
<br />
When it is ready you can enable the service<br />
<br />
# systemctl enable mdadm.service<br />
<br />
==Troubleshooting==<br />
If you are getting error when you reboot about "invalid raid superblock magic" and you have additional hard drives other than the ones you installed to, check that your hard drive order is correct. During installation, your RAID devices may be hdd, hde and hdf, but during boot they may be hda, hdb and hdc. Adjust your kernel line accordingly. This is what happened to me anyway.<br />
<br />
===Start arrays read-only===<br />
When an md array is started, the superblock will be written, and resync may begin. To start read-only set the kernel module {{ic|md_mod}} parameter {{ic|start_ro}}. When this is set, new arrays get an 'auto-ro' mode, which disables all internal io (superblock updates, resync, recovery) and is automatically switched to 'rw' when the first write request arrives.<br />
<br />
{{Note|The array can be set to true 'ro' mode using {{ic|mdadm -r}} before the first write request, or resync can be started without a write using {{ic|mdadm -w}}.}}<br />
<br />
To set the parameter at boot, add {{ic|<nowiki>md_mod.start_ro=1</nowiki>}} to your kernel line.<br />
<br />
Or set it at module load time from {{ic|/etc/modprobe.d/}} file or from directly from {{ic|/sys/}}.<br />
{{bc|echo 1 > /sys/module/md_mod/parameters/start_ro}}<br />
<br />
===Recovering from a broken or missing drive in the raid===<br />
You might get the above mentioned error also when one of the drives breaks for whatever reason. In that case you will have to fore the raid to still turn on even with one disk short. Type this (change where needed):<br />
# mdadm --manage /dev/md0 --run<br />
<br />
Now you should be able to mount it again with something like this (if you had it in fstab):<br />
# mount /dev/md0<br />
<br />
Now the raid should be working again and available to use, however with one disk short! So, to add that one disc partition it the way like described above in [[#Prepare_the_device|Prepare the device]]. Once that is done you can add the new disk to the raid by doing:<br />
# mdadm --manage --add /dev/md0 /dev/sdd1<br />
<br />
If you type:<br />
# cat /proc/mdstat<br />
you probably see that the raid is now active and rebuilding.<br />
<br />
You also might want to update your configuration (see: [[#Update configuration file]]).<br />
<br />
== Benchmarking ==<br />
There are several tools for benchmarking a RAID. The most notable improvement is the speed increase when multiple threads are reading from the same RAID volume.<br />
<br />
[http://sourceforge.net/projects/tiobench/ Tiobench] specifically benchmarks these performance improvements by measuring fully-threaded I/O on the disk.<br />
<br />
[http://www.coker.com.au/bonnie++/ Bonnie++] tests database type access to one or more files, and creation, reading, and deleting of small files which can simulate the usage of programs such as Squid, INN, or Maildir format e-mail. The enclosed [http://www.coker.com.au/bonnie++/zcav/ ZCAV] program tests the performance of different zones of a hard drive without writing any data to the disk.<br />
<br />
{{ic|hdparm}} should '''NOT''' be used to benchmark a RAID, because it provides very inconsistent results.<br />
<br />
== Additional Resources ==<br />
* [http://en.gentoo-wiki.com/wiki/RAID/Software RAID/Software] on the Gentoo Wiki<br />
* [http://en.gentoo-wiki.com/wiki/Software_RAID_Install Software RAID Install] on the Gentoo Wiki<br />
* [http://www.gentoo.org/doc/en/articles/software-raid-p1.xml Software RAID in the new Linux 2.4 kernel, Part 1] and [http://www.gentoo.org/doc/en/articles/software-raid-p2.xml Part 2] in the Gentoo Linux Docs<br />
* [http://raid.wiki.kernel.org/index.php/Linux_Raid Linux RAID wiki entry] on The Linux Kernel Archives<br />
* [http://linux-101.org/howto/arch-linux-software-raid-installation-guide Arch Linux software RAID installation guide] on Linux 101<br />
* [http://docs.redhat.com/docs/en-US/Red_Hat_Enterprise_Linux/6/html/Storage_Administration_Guide/ch-raid.html Chapter 15: Redundant Array of Independent Disks (RAID)] of Red Hat Enterprise Linux 6 Documentation<br />
* [http://tldp.org/FAQ/Linux-RAID-FAQ/x37.html Linux-RAID FAQ] on the Linux Documentation Project<br />
* [http://support.dell.com/support/topics/global.aspx/support/entvideos/raid?c=us&l=en&s=gen Dell.com Raid Tutorial] - Interactive Walkthrough of Raid<br />
* [http://www.miracleas.com/BAARF/ BAARF] including ''[http://www.miracleas.com/BAARF/RAID5_versus_RAID10.txt Why should I not use RAID 5?]'' by Art S. Kagel<br />
* [http://www.linux-mag.com/id/7924/ Introduction to RAID], [http://www.linux-mag.com/id/7931/ Nested-RAID: RAID-5 and RAID-6 Based Configurations], [http://www.linux-mag.com/id/7928/ Intro to Nested-RAID: RAID-01 and RAID-10], and [http://www.linux-mag.com/id/7932/ Nested-RAID: The Triple Lindy] in Linux Magazine<br />
* [http://www.cyberciti.biz/tips/linux-raid-increase-resync-rebuild-speed.html HowTo: Speed Up Linux Software Raid Building And Re-syncing]<br />
<br />
'''mdadm'''<br />
* [http://anonscm.debian.org/gitweb/?p=pkg-mdadm/mdadm.git;a=blob_plain;f=debian/FAQ;hb=HEAD Debian mdadm FAQ]<br />
* [http://www.kernel.org/pub/linux/utils/raid/mdadm/ mdadm source code]<br />
* [http://www.linux-mag.com/id/7939/ Software RAID on Linux with mdadm] in Linux Magazine<br />
<br />
'''Forum threads'''<br />
* [http://forums.overclockers.com.au/showthread.php?t=865333 Raid Performance Improvements with bitmaps]<br />
* 2011-08-28 - Arch Linux - [https://bbs.archlinux.org/viewtopic.php?id=125445 GRUB and GRUB2]<br />
* 2011-08-03 - Arch Linux - [https://bbs.archlinux.org/viewtopic.php?id=123698 Can't install grub2 on software RAID]<br />
* 2011-07-29 - Gentoo - [http://forums.gentoo.org/viewtopic-t-888624-start-0.html Use RAID metadata 1.2 in boot and root partition]<br />
<br />
'''RAID with encryption'''<br />
* [http://www.shimari.com/dm-crypt-on-raid/ Linux/Fedora: Encrypt /home and swap over RAID with dm-crypt] by Justin Wells</div>Fabertawe