Raid
test
Hard Drives
A software RAID array will be automatically configured as part of the installation process for servers which contain multiple hard drives. This is to ensure redundancy, so if one disk fails the system will still function.
The specifics of the RAID setup depends on the number of drives available, to balance redundancy and capacity.
The root and swap volumes are configured using LVM on the RAID device /dev/md1 as follows:
- 1 drive - no RAID
- 2 drives - RAID 1
- 3 drives - RAID 1 + hot spare
- 4 drives - RAID 6
- 5+ drives - RAID 6 + hot spare
The /boot volume and EFI partition if necessary is always a non-LVM RAID 1 array on the device /dev/md0.
If you use a hardware RAID controller to manage your drives, this should be configured to present a single volume, which SME will configure without software RAID.
Default RAID Rationale
The differences in RAID layout between SME Server 10 and previous versions is summarised below:
| Number of Drives | SME Server 10 | Previous Versions |
|---|---|---|
| 1 | No software RAID | Degraded RAID 1 |
| 2 | Software RAID 1 | |
| 3 | RAID 1 + hot spare | |
| 4 | RAID 6 | RAID 5 + hot spare |
| 5 | RAID 6 + hot spare | |
| 6 | ||
| 7+ | RAID 6 + hot spare | |
The main differences are no degraded RAID 1 for a single disk install, which better supports virtualised and hardware RAID use cases, and a preference for RAID 6 over RAID 5. This is to reduce the risk of a single disk failure bringing down the array. While consumer hard drives have got significantly larger over time, their unrecoverable read error rate (URE) has remained at 1 per 10^14 bits, or 12TB. As an example, imagine a server with 5 x 4TB drives. Under previous versions of SME Server this would have been configured as a 4 disk RAID 5 array with 1 hot spare. If one drive failed, the hot spare would become active and the array would begin to rebuild. This would require reading all 3 disks and, at some point during that 12TB operation, it’s very likely that an unrecoverable error would be encountered. At this point, the whole array would fail. In comparison, a RAID 6 array is tolerant to two disk failures. While this does not entirely solve the risk of a URE during rebuild, it significantly reduces the likelihood of it taking down the array. Note: RAID is a convenient method of protecting server availability from a drive failure. It does not remove the need for regular backups, which can be configured using the Server Manager.
Disk Layout
Mirroring drives in the same IDE channel (eg. hda and hdb) is not desirable. If that channel goes out, you may lose both drives. Also, performance will suffer slightly.
The preferred method is to use the primary location on each IDE channel (eg. hda and hdc). This will ensure that if you lose one channel, the other will still operate. It will also give you the best performance.
In a 2 drive setup put each drive on a different IDE channel:
IDE 1 Primary - Drive 1
IDE 1 Secondary - CDROM
IDE 2 Primary - Drive 2
Obviously this section is obsolete with SATA hard drives because each disk has its own channel.
Identifying Hard Drives
It may not always be obvious which physical hard drive maps to which logical device. The first step would be to be able to identify all block devices present on your server. This could be done by using two commands
lsblk
or the following
findmnt
Then, once you identified a block device , the simplest method to verify which physical drive it is, is using S.M.A.R.T. capability to map the serial number on the physical package with that displayed by smartctl. Assuming the device of interest is sda, (a SCSI drive), then you would issue the following command as root:
smartctl -i /dev/sda
Or if an IDE Drive
smartctl -i /dev/hda
Adding Additional Drives
For servers which were installed with 2+ drives and have a working RAID array, it is possible to add an additional drive which will become a hot spare, ready to be activated in case of drive failure.
See also AddExtraHardDisk. It's an alternative for part of the data if you have only one drive and you want to use RAID1. But better solution is to reinstall SME10 with 2 drives.
Ensure that any new drives are the same size or larger than your existing drives.
- Shut down the machine
- Install one additional drive at a time
- Boot up
- At the login prompt log on as admin with the root password to get to the admin console
- Go to #5 Manage disk redundancy
- Accept the option to add an additional drive
If the Manage disk redundancy page displays the message "The free disk count must equal one" and "Manual intervention may be required", then you probably have additional hard drives that need to be disconnected while the RAID is set up. An external USB drive will have this effect, and should be unplugged.
Reusing Hard Drives
- MBR formatted disks
If it was ever installed on a Windows machine, or any of the *BSDs, (or in some cases an old system with RAID and/or LVM) then you will need to clear the MBR first before installing it.
From the linux command prompt, type the following:
#dd if=/dev/zero of=/dev/hdx bs=512 count=1
or
#dd if=/dev/zero of=/dev/sdx bs=512 count=1
You MUST reboot so that the empty partition table gets read correctly.
For more information, check: http://bugs.contribs.org/show_bug.cgi?id=2154
- For disks previously formatted as GPT this is insufficient. It's probably best to use gdisk or parted or partx to delete the partitions; there are other tools that will work. Parted has limited support for LVM.
Upgrading the Hard Drive Size
Note: these instructions are only applicable if you have a RAID system with more than one drive. They are not applicable to a single-drive RAID 1 system, and increasing the useable space on such a system by cloning the existing single drive to a larger drive is not supported. See http://bugs.contribs.org/show_bug.cgi?id=5311
- CAUTION MAKE A FULL BACKUP!
- Ensure you have e-smith-base-4.16.0-33 or newer installed. [or Update to at least 7.1.3]
HD Scenario - Current 250gb drives, new larger 500gb drives
- Shut down and install one larger drive in system for one old HD. Unplug any USB-connected drives.
- Boot up and login to the admin console and use option 5 to add the new (larger) drive to system.
- Wait for raid to fully sync.
- Repeat steps 1-3 until all drives in system are upgraded to larger capacity.
- Ensure all drives have been replace with larger drives and array is in sync and redundant!
- Issue the following commands:
mdadm --grow /dev/md2 --size=max pvresize /dev/md2 lvresize -l +100%FREE main/root ext2online -C0 /dev/main/root
In the last command above, the -C0 is: dash C zero
If you receive an "command not found" error, try this:
resize2fs /dev/mapper/main-root &
TIP: I put an "&" at end to allow it to run in background even if I close ssh session.
Notes :
- All of this can be done while the server is up and running with the exception of #1.
- These instructions should work for any raid level you have as long as you have >= 2 drives
- If you have disabled lvm , you don't need the pvresize or lvresize command, therefore the final line becomes
ext2online -C0 /dev/md2 #(or whatever / is mounted to)
or If you receive an "command not found" error, try this:
resize2fs /dev/md2 &
Replacing and Upgrading a Hard Drive after HD fail
Note: See Bugzilla: 6632 and Bugzilla:6630 a suggested sequence for Upgrading a Hard Drive size is detailed after issue when attempting to sync a new drive when added first as sda.
Note: These instructions are applicable if you have a faulty HD on a RAID system with more than one drive and intend to upgrade the sizes as well as replacing the failed HD. They are not applicable to a single-drive RAID 1 system, and increasing the useable space on such a system by cloning the existing single drive to a larger drive is not supported. See http://bugs.contribs.org/show_bug.cgi?id=5311
- CAUTION MAKE A FULL BACKUP!
- Ensure you have e-smith-base-4.16.0-33 or newer installed. [or Update to at least 7.1.3]
HD Scenario - Current 250gb drives, new larger 500gb drives
- Remove failed HDD from system, ensure remaining drive is on sda on its own and boot up.
- Shutdown, connect one new 500gb drive as sdb and boot up
- Login to the admin panel and manage raid to add new (larger) drive to system.
- Wait for raid to fully sync
- Do full reboot with those 2 drives in place (1 original, 1 new)
- Shutdown again, disconnect the original drive, and connect the new drive just sync'd as sda (in place of original)
- Boot up again with just the one new drive in place, and confirm it boots OK.
- Shutdown, and connected the other 500gb drive as sdb
- Boot up login to admin panel and add sdb to the array, and wait for raid to fully sync.
- Reboot and ensure all drives have been replaced with larger drives and array is in sync and redundant!
- Issue the following commands:
mdadm --grow /dev/md2 --size=max pvresize /dev/md2 lvresize -l +100%FREE main/root ext2online -C0 /dev/main/root
In the last command above, the -C0 is: dash C zero
If you receive an "command not found" error, try this:
resize2fs /dev/mapper/main-root &
TIP: I put an "&" at end to allow it to run in background even if I close ssh session.
Notes :
- These instructions should work for any raid level you have as long as you have >= 2 drives
- If you have disabled lvm , you don't need the pvresize or lvresize command, therefore the final line becomes
ext2online -C0 /dev/md2 #(or whatever / is mounted to)
or If you receive an "command not found" error, try this:
resize2fs /dev/md2 &
RAID Notes
Many on-board hardware raid cards are in fact software RAID. Turn it off as cheap "fakeraid" cards aren't good for Linux. You will generally get better performance and reliability with Linux Software RAID (http://linux-ata.org/faq-sata-raid.html). Linux software RAID is fast and robust.
If you are insistent on getting a hardware RAID, buy a well supported RAID card which has a proper RAID BIOS. This hides the disks and presents a single disk to Linux (http://linuxmafia.com/faq/Hardware/sata.html). Please check that it is supported by the kernel and has some form of management. Also avoid anything which requires a driver. Try googling for the exact model of RAID controller before buying it. Please note that you won't get a real hardware raid controller cheap.
It rarely happens, but sometimes when a device has finished rebuilding, its state doesn't change from "dirty" to "clean" until a reboot occurs. This is cosmetic
Periodic scrub of RAID arrays
A Periodic scrub of RAID arrays (weekly raid check) is performed every week on Sunday at 04:22 local time, refer Bugzilla:3535 and Bugzilla:6160 for more information.
Theses operations are logged, however, no emails will be sent to admin as of the release of packages associated with Bug #6160 or the release of the 8.1 ISO.
Receive periodic check of RAID by email
There are routines in SME Server to check the RAID and sent mail to the admin user, when the RAID is degraded or when the RAID is resynchronizing. But the admin user may receive a lot of emails and sometimes messages can be forgotten. So the purpose is to have a routine which sends email to the user of your choice each week.
nano /etc/cron.weekly/raid-status.sh
You have to change the variable DEST="stephane@your-domaine-name.org" to the email you decide to use.
#!/bin/sh # cron.weekly/mdadm-status -- weekly status of the RAID # 2013 Pierre-Alain Bandinelli # distributed under the terms of the Artistic Licence 2.0 # Get status from the RAID array and send the details by email. # Email will go to the address specified in the commandline. set -eu MDADM=/sbin/mdadm [ -x $MDADM ] || exit 0 # package may be removed but not purged DEST="stephane@your-domaine-name.org" exec $MDADM --detail $(ls /dev/md*) | mail -s "RAID status SME Server" $DEST
save by ctrl+x
chmod +x /etc/cron.weekly/raid-status.sh
each sunday a 4h00 AM you will receive a mail which looks to this :
/dev/md1:
Version : 0.90
Creation Time : Sun Jan 6 20:50:41 2013
Raid Level : raid1
Array Size : 104320 (101.89 MiB 106.82 MB)
Used Dev Size : 104320 (101.89 MiB 106.82 MB)
Raid Devices : 2
Total Devices : 2
Preferred Minor : 1
Persistence : Superblock is persistent
Update Time : Sun Dec 22 04:22:42 2013
State : clean
Active Devices : 2
Working Devices : 2
Failed Devices : 0
Spare Devices : 0
UUID : 28745adb:d9cff1f4:fcb31dd8:ff24cb0c
Events : 0.208
Number Major Minor RaidDevice State
0 8 1 0 active sync /dev/sda1
1 8 17 1 active sync /dev/sdb1
/dev/md2:
Version : 0.90
Creation Time : Sun Jan 6 20:50:42 2013
Raid Level : raid1
Array Size : 262036096 (249.90 GiB 268.32 GB)
Used Dev Size : 262036096 (249.90 GiB 268.32 GB)
Raid Devices : 2
Total Devices : 2
Preferred Minor : 2
Persistence : Superblock is persistent
Update Time : Sun Dec 22 05:30:36 2013
State : clean
Active Devices : 2
Working Devices : 2
Failed Devices : 0
Spare Devices : 0
UUID : c343c79e:91c01009:fcde78b4:bad0b497
Events : 0.224
Number Major Minor RaidDevice State
0 8 2 0 active sync /dev/sda2
1 8 18 1 active sync /dev/sdb2
If you want to test the message sent without waiting the next sunday, you can do
/etc/cron.weekly/raid-status.sh
nospare
If you use the commandline parameter nospare during installation ("sme nospare"), the system will still count the missing spare towards the number of drives. A system with 6 physically present harddrives thus will be formated Raid6 _not_ Raid5. Resulting capacity of course will be "n-2". Note: with the release of version 7.6 and 8.0, the commandline parameter "sme nospare" has been changed to "sme spares=0" . In addition, you may also select the number of spare(s) implemented [0,1,or 2].
remove the degraded RAID message
When you install the smeserver with one drive with a degraded raid, you will see a 'U_' state but without warnings. If you want to leave just one 'U' in the /proc/mdstat and stop all future questions about your degraded raid state, then :
mdadm --grow /dev/md0 --force --raid-devices=1 mdadm --grow /dev/md1 --force --raid-devices=1
after that you will see this
# cat /proc/mdstat
Personalities : [raid1]
md0 : active raid1 sda1[0]
255936 blocks super 1.0 [1/1] [U]
md1 : active raid1 sda2[0]
268047168 blocks super 1.1 [1/1] [U]
bitmap: 2/2 pages [8KB], 65536KB chunk
unused devices: <none>
Resynchronising a Failed RAID
Sometimes a partition will be taken offline automatically. Admin will receive an email DegradedArray event on /dev/md2.
smartctl -a /dev/hda
Where hda is the device to be checked; check all of them.
You may check the health of your array using the Admin Console. Login as root, type console. Select Item 5. "Manage disk reduncancy"
--------Disk Reduncancy status as of Thursday Dec 22 -------
Current RAID status:
Personalities : [raid1]
md2 : active raid1 hda2[0] <-- NOTICE hdb2[#] is missing. Means hdb2[#] failed.
38973568 blocks [2/1] [U_]
md1 : active raid1 hda1[0] hdb1[1]
104320 blocks [2/2] [UU]
unused devices: <none>
Only Some of the RAID devices are unclean. <-- NOTICE This message and
Manual intervention may be required. <-- this message.
Notice the last 2 sentences of the window above. You have some problems.
If your system is healthy however the message you will see at the bottom of Raid Console window is:
All RAID devices are in clean state
If you have no software RAID devices you will see the message at the bottom of the Console window:
Your system only has a single disk drive installed or is using hardware
mirroring. If you would like to enable software mirroring, please shut
down, install a second disk drive (of the same capacity) and then return
to this screen.
Additionally, the details of the raid can be seen by inspecting the mdstat file from the shell prompt.
[root@sme]# cat /proc/mdstat
Personalities : [raid1]
md1 : active raid1 hda3[0] hdb3[1]
38837056 blocks [2/2] [UU]
md2 : active raid1 hdb2[1] <-- Shows current active partition - note there is one missing
1048704 blocks [2/1] [_U] <-- '_' = partition missing from array
md0 : active raid1 hda1[0] hdb1[1]
255936 blocks [2/2] [UU]
Make a note of the raid partition that has failed, shown by [_U]
In this case it is md2, the device being /dev/md2.
The failed drive partition is indicated by the '_' underline character. In the above example _U indicates that the first drive partition on md2, (Multi-Device 2) has failed. The second drive partition on md2, symbolized by the character 'U' is still part of the md2. If the second drive partition had failed, that is hdb2 then the details would be reversed. E.g. [U_] . Placing the _ Underline second in the details.
Determine the missing physical partition, Look carefully at the sample above and fill in the gap for which drive is missing.
In this example, it's hda2, the device being /dev/hda2
md1 : active raid1 hda3[0] hdb3[1] md2 : active raid1 hda2[0] hdb2[1] <--- In the above sample hda2[0] is missing md0 : active raid1 hda1[0] hdb1[1]
If the raid has a failed disk that has not yet been kicked out of the array then mdstat will show something like the following:
md2 : active raid1 hda2[0](F) hdb2[1] <-- Shows current active partition - with one FAILED (F)
1048704 blocks [2/1] [_U] <-- '_' = partition missing from array
In this case before you add the disk back in you will need to remove the disk as per:
[root@sme]# mdadm --remove /dev/md2 /dev/hda2
However if the drive has already been removed by the operating system then removing the drive is unnecessary. To determine this use the command:
mdadm --query --detail /dev/md2
Of course use the proper md# based on your configuration. This command will give you several lines of data, including the size of the array. Near the end of the output you will see the following if the drive has been removed already. There is no need to remove the drive since it has already been removed.
Number Major Minor RaidDevice State
0 3 2 0 active sync /dev/hda2
1 0 0 - removed <-- NOTE THIS
To add the physical partition back and rebuild the raid partition.
[root@sme]# mdadm --add /dev/md2 /dev/hda2
Once you type the command the following message will appear, appropriate for your device.
[root@sme] mdadm: hot added /dev/hda2
It important to know that your devices are likely to be different, E.G your device could be /dev/sda2 or you may have more than two disks, including a hot standby. These details can always be determined from the mdstat file. Once the raid resync has been started, the progress will be noted in mdstat. You can see this real time by:
[root@sme]# watch -n .1 cat /proc/mdstat
or you can see this in a snapshot by:
[root@sme]# cat /proc/mdstat
Personalities : [raid1]
md1 : active raid1 hda3[0] hdb3[1]
38837056 blocks [2/2] [UU]
md2 : active raid1 hda2[2] hdb2[1]
1048704 blocks [2/1] [_U]
[=>...................] recovery = 6.4% (67712/1048704) finish=1.2min speed=13542K/sec
md0 : active raid1 hda1[0] hdb1[1]
255936 blocks [2/2] [UU]
When recovery is complete, the partitions will all be up:
[root@sme]# cat /proc/mdstat
Personalities : [raid1]
md1 : active raid1 hda3[0] hdb3[1]
38837056 blocks [2/2] [UU]
md2 : active raid1 hda2[0] hdb2[1]
1048704 blocks [2/2] [UU]
md0 : active raid1 hda1[0] hdb1[1]
255936 blocks [2/2] [UU]
If this action is required regularly, you should test your disks for SMART errors and physical errors, check your disk cables, and make sure no two hard drives share the same IDE port. See also: http://wiki.contribs.org/Monitor_Disk_Health
Also check your driver cards, since a faulty card can destroy the data on a full RAID set as easily as it can a single disk.
Convert Software RAID1 to RAID5
- Login as root
- Move to /boot (we must create a new initrd image to load raid5 driver). cd /boot
- Make a backup copy mv initrd-`uname -r`.img initrd-`uname -r`.img.old
- Create the new image mkinitrd --preload raid5 initrd-`uname -r`.img `uname -r`
- Shut down and install new drive(s) in system.
- Boot up with SME cd and enter the rescue mode. sme rescue
- Skip network setup.
- Skip mounting the current SME installation.
- Now, create on the new drive(s) the correct partition table. sfdisk -d /dev/sda > tmp.out sfdisk /dev/sdc < tmp.out
- Repeat the last step for each new hd (sdd, sde etc.).
- Create the new array mdadm --create /dev/md2 -c 256 --level=5 --raid-devices=2 /dev/sda2 /dev/sdb2 mdadm: /dev/sda2 appears to be part of a raid array: level=raid1 devices=2 ctime=Fri Dec 18 13:17:49 2009 mdadm: /dev/sdb2 appears to be part of a raid array: level=raid1 devices=2 ctime=Fri Dec 18 13:17:49 2009 Continue creating array? y mdadm: array /dev/md2 started.
- Wait for resync; monitor the status with cat /proc/mdstat root# cat /proc/mdstat Personalities : [raid0] [raid1] [raid5] md2 : active raid5 sdb1[2] sda1[0] 1048512 blocks level 5, 256k chunk, algorithm 2 [2/1] [U_] [==>..................] recovery = 12.5% (132096/1048512) finish=0.8min speed=18870K/sec
- Reboot exit
- Login as root
- Add the new drives to the array mdadm --add /dev/md2 /dev/sdc2
- Repeat the last step for each new hd (sdd2, sde2 etc.)
- Grow the array mdadm --grow /dev/md2 --raid-devices=N
- N is the total number of drives: minimum is 3
- Wait for array reshaping. This part can take a substantial amount of time; monitor it with cat /proc/mdstat root# cat /proc/mdstat Personalities : [raid0] [raid1] [raid5] md2 : active raid5 sdc1[2] sdb1[1] sda1[0] 1048512 blocks super 0.91 level 5, 256k chunk, algorithm 2 [3/3] [UUU] [==>..................] reshape = 12.5% (131520/1048512) finish=2.5min speed=5978K/sec
- Issue the following commands: pvresize /dev/md2 lvresize -l +100%FREE main/root resize2fs /dev/main/root
Notes :
- If you have disabled lvm
- you don't need the pvresize or lvresize command
- the final line becomes resize2fs /dev/md2 (or whatever / is mounted to)
- More info: http://www.arkf.net/blog/?p=47
Add another Raid to mount to /home/e-smith/files
this is inspired from previous content of AddExtraHardDisk and particularly the part AddExtraHardDisk#Additional steps to create a raid array from multiple disks but updated to 2022 and SME10
1 you need to check what disk you want, using lsblk
# lsblk --fs
NAME FSTYPE LABEL UUID MOUNTPOINT
sda
├─sda1 vfat B93A-85A4 /boot/efi
├─sda2 xfs 89e9cc9e-d3d2-4d02-bad5-2698aea0a510 /boot
├─sda3 swap 64d21f89-4d7c-417a-907e-34236f6cd0be [SWAP]
└─sda4 xfs 65bf712c-2186-4524-aae8-edd8151de1e7 /
sdb
sdc
then you can create the Raid array. We assume you only need onethen you need to rebuild the grub.conf, depending on your system is EFI or legacy use the appropriate command#EFI
grub2-mkconfig -o /boot/efi/EFI/centos/grub.cfg #Legacy grub2-mkconfig -o /boot/grub2/grub.cfg
Raid partition, and hence do not need to partition it.
#create array
mdadm --create --verbose /dev/md11 --level=1 --raid-devices=2 /dev/sdb /dev/sdc
# add to mdadm.conf
mdadm --detail --scan --verbose /dev/md11 >> /etc/mdadm.conf
then format it and enable quotas. If you want to add a LVM Layer, this is just before that !
mkfs.xfs /dev/md11
now you have
# lsblk --fs
NAME FSTYPE LABEL UUID MOUNTPOINT
sda
├─sda1 vfat B93A-85A4 /boot/efi
├─sda2 xfs 89e9cc9e-d3d2-4d02-bad5-2698aea0a510 /boot
├─sda3 swap 64d21f89-4d7c-417a-907e-34236f6cd0be [SWAP]
└─sda4 xfs 65bf712c-2186-4524-aae8-edd8151de1e7 /
sdb linux_raid_member localhost.localdomain:11 6c4b9640-7349-15fe-28b1-78843d9a149a
└─md11 xfs 0ab4fe2a-aa81-4728-90d8-2f96d4624af8
sdc linux_raid_member localhost.localdomain:11 6c4b9640-7349-15fe-28b1-78843d9a149a
└─md11 xfs 0ab4fe2a-aa81-4728-90d8-2f96d4624af8
then you need to mount it temporary to move your content
mkdir /mnt/newdisk
mount /dev/md11 /mnt/newdisk
rsync -arv /home/e-smith/files/ /mnt/newdisk
When happy with result simply add an entry to you fstab, according to last lsblk output in this case you should add
UUID=0ab4fe2a-aa81-4728-90d8-2f96d4624af8 /home/e-smith/files xfs uquota,gquota 0 0
To have the disk mounted on reboot, you need to alter grub
vim /etc/default/grub
and alter the command line to add either "rd.md=1 rd.md.conf=1 rd.auto=1" or specifically add the uuid to mount (obviously if you add a LVM layer you will rather need to add something like rd.lvm.lv=mylvm/video rd.lvm.lv=mylvm/files)
1GRUB_TIMEOUT=5
2GRUB_DISTRIBUTOR="$(sed 's, release .*$,,g' /etc/system-release)"
3GRUB_DEFAULT=saved
4GRUB_DISABLE_SUBMENU=true
5GRUB_TERMINAL_OUTPUT="gfxterm"
6GRUB_CMDLINE_LINUX="rhgb quiet rootflags=uquota,pquota rd.md=1 rd.md.conf=1 rd.auto=1"
7GRUB_DISABLE_RECOVERY="false"
8GRUB_BACKGROUND="/boot/grub2/smeserver10.png"
9GRUB_GFXMODE="1024x768"
10GRUB_THEME="/boot/grub2/themes/koozali/theme.txt"
then you need to make sure dracut will add the drivers
vim /etc/dracut.conf
and alter the line needed (you probably will need to uncomment this line and add mdraid between the quote)
19# dracut modules to add to the default
20add_dracutmodules+="mdraid"
Finally rebuild the initfs
cp /boot/initramfs-$(uname -r).img /boot/initramfs-$(uname -r).img.old
dracut --add="mdraid" /boot/initramfs-$(uname -r).img $(uname -r)
Copy data from one disk of an old Raid mirror disk
Let's say you want to copy the huge amount of data you excluded from the backup to migrate from SME9 to SME10 and now you want to copy this to your new server.
This How-To assume your current install is without LVM. An extra trick is needed if you have a LVM and previous SME9 also. You simply need to rename the vg group either of the old SME or new one using a rescue disk or another Linux distro, see UpgradeDisk#Moving from SME 8.x to SME 9.x.
- put one of the old drives in the server or in an external case and connect it
- use lsblk to identify the drive
- adapt the following commands
# lsblk
sdd 8:48 0 931,5G 0 disk
├─sdd1 8:49 0 250M 0 part
└─sdd2 8:50 0 931,3G 0 part
We assume that sd1 was the boot partition and the stuff we want is in sdd2
#assemble and run on degraded
mdadm -A /dev/md126 /dev/sdd2 --run
now let's try to mount, it will work only if you had no LVM, or it will return this
# mkdir /mnt/olddisk/
# mount /dev/md126 /mnt/olddisk/
mount: filesystem « LVM2_member » unknown
you can skip this step if you did not got the LVM error. Then we need to activate the LVM, and we can assume you might need also to install lvm stuffs...
# yum install lvm2 -y
vgchange -a y main
mount /dev/mapper/main-root /mnt/olddisk/
It is now time to copy your stuffs.
rsync -arvHAX /mnt/olddisk/home/e-smith/files/ /home/e-smith/files
then to remove safely your disk
umount /dev/mapper/main-root
vgchange -a n main
mdadm --stop /dev/md126
