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Source of this page is the [https://raid.wiki.kernel.org/index.php/Growing raid wiki]
Source of this page is the [https://raid.wiki.kernel.org/index.php/Growing raid wiki]
The purpose is to add a new drive to an existing Raid5 with LVM which is the standard installation of SME Server. Please backup your datas before to start this HOWTO, '''you may loose them'''.
==Growing an existing Array==
When new disks are added, existing raid partitions can be grown to use the new disks. After the new disk was partitioned, the RAID level 1/4/5 array can be grown. Assuming that before growing it contains four drives in Raid5 and therefore an array of 3 drives (3*10G) and 1 spare drive(10G). See this [[http://wiki.contribs.org/Raid#Hard_Drives_.E2.80.93_Raid|HowTo]] for understanding the automatic raid construction of SME Server
{{Note box|due to a bug of kernel 2.6.18 which is the default kernel of Centos5 and SME Server 8.0, you can not grow a RAID6}}
When new disks are added, existing raid partitions can be grown to use the new disks. After the new disk was partitioned, the RAID level 1/4/5 array can be grown. Assuming that before growing it contains four drives in Raid5 and therefore an array of 3 drives (3*10G) and 1 spare drive(10G). See this [[Raid#Hard_Drives_.E2.80.93_Raid|HowTo]] for understanding the automatic raid construction of SME Server
This is how your array looks before.
This is how your array looks before.
md2 : '''active raid5''' sdd2[8](S) sdc2[2] sdb2[1] sda2[0]
md2 : '''active raid5''' sdd2[8](S) sdc2[2] sdb2[1] sda2[0]
72644096 blocks level 5, 256k chunk, algorithm 2 [8/8] [UUU]
72644096 blocks level 5, 256k chunk, algorithm 2 [8/8] [UUU]
===Partition the new drive===
for example using this command to partition the new drive
for example using this command to partition the new drive
sfdisk -d /dev/sda > sfdisk_sda.output
sfdisk -d /dev/sda > sfdisk_sda.output
sfdisk -f /dev/sde < sfdisk_sda.output
sfdisk -f /dev/sde < sfdisk_sda.output
If you have errors about sfdisk command, you can clean the drive with the dd command. Be aware that dd is called data-destroyer, think about which partition you type.
If you have errors about sfdisk command, you can clean the drive with the dd command.
{{Warning box|Be aware that dd is called data-destroyer, think about which partition you type.}}
#dd if=/dev/zero of=/dev/sdX bs=512 count=1
#dd if=/dev/zero of=/dev/sdX bs=512 count=1
===Adding partitions===
Now we need to add the first partition /dev/sde1 to /dev/md1
Now we need to add the first partition /dev/sde1 to /dev/md1
[root@smeraid5 ~]# mdadm --grow --raid-devices='''5''' /dev/md1
[root@smeraid5 ~]# mdadm --grow --raid-devices='''5''' /dev/md1
Here we use the option --raid-devices='''5''' because the raid1 use all drives. You can see how the array is
[root@smeraid5 ~]# mdadm --detail /dev/md1
[root@smeraid5 ~]# mdadm --detail /dev/md1
After that we have to do the same thing with the md2 which is a raid5 array.
After that we have to do the same thing with the md2 which is a raid5 array.
[root@smeraid5 ~]# mdadm --add /dev/md2 /dev/sdj2
[root@smeraid5 ~]# mdadm --add /dev/md2 /dev/sde2
mdadm: added /dev/sdj2
mdadm: added /dev/sde2
[root@smeraid5 ~]# mdadm --grow --raid-devices='''4''' /dev/md2
[root@smeraid5 ~]# mdadm --grow --raid-devices='''4''' /dev/md2
mdadm: ... critical section passed.
mdadm: ... critical section passed.
{{tip box| For md2 you have to keep --raid-devices='''4''' if you want to have an array of 4 drives+1spare, if you do not want a spare drive, you should set --raid-devices='''5'''}}
{{tip box|msg=You need to keep --raid-devices='''4''' if you want to have an array of 4 drives+1spare, However if you do not want a spare drive, you should set --raid-devices='''5'''}}
we can take a look to the md2 array
we can take a look to the md2 array
[root@smeraid5 ~]# mdadm --detail /dev/md2
[root@smeraid5 ~]# mdadm --detail /dev/md2
/dev/md2:
/dev/md2:
Raid Level : raid5
Raid Level : raid5
Array Size : 32644096 (30.28 GiB 31.39 GB)
Array Size : 32644096 (30.28 GiB 31.39 GB)
Used Dev Size : 10377728 (7.90 GiB 9.63 GB)
Used Dev Size : 7377728 (7.90 GiB 9.63 GB)
Raid Devices : 4
Raid Devices : 4
Total Devices : 5
Total Devices : 5
Preferred Minor : 2
Preferred Minor : 2
Persistence : Superblock is persistent
Persistence : Superblock is persistent
Update Time : Tue Oct 29 21:39:29 2013
Update Time : Tue Oct 29 21:39:29 2013
State : clean
State : clean
Failed Devices : 0
Failed Devices : 0
Spare Devices : 1
Spare Devices : 1
Layout : left-symmetric
Layout : left-symmetric
Chunk Size : 256K
Chunk Size : 256K
UUID : d2c26bed:b5251648:509041c5:fab64ab4
UUID : d2c26bed:b5251648:509041c5:fab64ab4
Events : 0.462
Events : 0.462
Number Major Minor RaidDevice State
Number Major Minor RaidDevice State
0 8 2 0 active sync /dev/sda2
0 8 2 0 active sync /dev/sda2
3 8 34 2 active sync /dev/sdd2
3 8 34 2 active sync /dev/sdd2
4 8 50 3 active sync /dev/sde2
4 8 50 3 active sync /dev/sde2
2 8 114 - spare /dev/sdc2
2 8 114 - spare /dev/sdc2
===LVM: Growing the PV===
Once the construction is done, we have to set the LVM to use the whole space
Once the construction is done, we have to set the LVM to use the whole space
You should verify that your LVM use the whole drive space with the command
You should verify that your LVM use the whole drive space with the command
[root@smeraid5 ~]# pvdisplay
[root@smeraid5 ~]# pvdisplay
--- Physical volume ---
--- Physical volume ---
[root@smeraid5 ~]# lvdisplay
[root@smeraid5 ~]# lvdisplay
<noinclude>[[Category:Howto]][[Category:Administration:Storage]]</noinclude>
