Raid:Growing

	Work in Progress:
	This page is a Work in Progress. The contents off this page may be in flux, please have a look at this page history the to see list of changes.

Source of this page is the raid wiki

Adding partitions

	Note:
	due to a bug of kernel 2.6.18 which is the default kernel of Centos5 and SME Server 8.0, you can not grown 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 [[1]] for understanding the automatic raid construction of SME Server

This is how your array looks before.

[root@smeraid5 ~]# cat /proc/mdstat
Personalities : [raid6] [raid5] [raid4] [raid1] 
md1 : active raid1 sda1[0] sdb1[1] sdc1[2] sdd1[3]
     104320 blocks [4/4] [UUUU]
     
md2 : active raid5 sdd2[8](S) sdc2[2] sdb2[1] sda2[0]
     72644096 blocks level 5, 256k chunk, algorithm 2 [8/8] [UUU]

for example using this command to partition the new drive

sfdisk -d /dev/sda > 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.

#dd if=/dev/zero of=/dev/sdX bs=512 count=1

Now we need to add the first partition /dev/sde1 to /dev/md1

[root@smeraid5 ~]# mdadm --add /dev/md1 /dev/sde1
mdadm: added /dev/sde1
[root@smeraid5 ~]# mdadm --grow --raid-devices=5 /dev/md1

you can see how the array is

[root@smeraid5 ~]# mdadm --detail /dev/md1
/dev/md1:
       Version : 0.90
 Creation Time : Tue Oct 29 21:04:15 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 : 5
 Total Devices : 5
Preferred Minor : 1
   Persistence : Superblock is persistent

   Update Time : Tue Oct 29 21:39:00 2013
         State : clean
Active Devices : 5
Working Devices : 5
Failed Devices : 0
 Spare Devices : 0

          UUID : 15eb70b1:3d0293bb:f3c49d70:6fc5aa4d
        Events : 0.4

   Number   Major   Minor   RaidDevice State
      0       8        1        0      active sync   /dev/sda1
      1       8       17        1      active sync   /dev/sdb1
      2       8       33        2      active sync   /dev/sdc1
      3       8       49        3      active sync   /dev/sdd1
      4       8       65        4      active sync   /dev/sde1

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
mdadm: added /dev/sdj2

[root@smeraid5 ~]# mdadm --grow --raid-devices=4 /dev/md2
mdadm: Need to backup 14336K of critical section..
mdadm: ... critical section passed.

	Tip:
	Add Tip here

we can take a look to the md2 array

[root@smeraid5 ~]# mdadm --detail /dev/md2
/dev/md2:
       Version : 0.90
 Creation Time : Tue Oct 29 21:04:28 2013
    Raid Level : raid5
    Array Size : 32644096 (30.28 GiB 31.39 GB)
 Used Dev Size : 10377728 (7.90 GiB 9.63 GB)
  Raid Devices : 4
 Total Devices : 5
Preferred Minor : 2
   Persistence : Superblock is persistent

   Update Time : Tue Oct 29 21:39:29 2013
         State : clean
Active Devices : 4
Working Devices : 5
Failed Devices : 0
 Spare Devices : 1

        Layout : left-symmetric
    Chunk Size : 256K

          UUID : d2c26bed:b5251648:509041c5:fab64ab4
        Events : 0.462

   Number   Major   Minor   RaidDevice State
      0       8        2        0      active sync   /dev/sda2
      1       8       18        1      active sync   /dev/sdb2
      3       8       34        2      active sync   /dev/sdd2
      4       8       50        3      active sync   /dev/sde2

      2       8      114        -      spare   /dev/sdc2

Once the construction is done, we have to set the LVM to use the whole space

[root@smeraid5 ~]# pvresize /dev/md2

 Physical volume "/dev/md2" changed
 1 physical volume(s) resized / 0 physical volume(s) not resized

after that we can resize the LVM

[root@smeraid5 ~]# lvresize -l +100%FREE  /dev/main/root
 Extending logical volume root to 30,25 GB
 Logical volume root successfully resized

	Tip:
	/dev/main/root is the default name, but if you have changed this you can find it by typing the command : lvdisplay

[root@smeraid5 ~]# resize2fs  /dev/main/root
resize2fs 1.39 (29-May-2006)
Filesystem at /dev/main/root is mounted on /; on-line resizing required
Performing an on-line resize of /dev/main/root to 19726336 (4k) blocks.

You should verify that your LVM use the whole drive space with the command

[root@smeraid5 ~]# pvdisplay
 --- Physical volume ---
 PV Name               /dev/md2
 VG Name               main
 PV Size               30.25 GB / not usable 8,81 MB
 Allocatable           yes (but full)
 PE Size (KByte)       32768
 Total PE              1533
 Free PE               0
 Allocated PE          1533
 PV UUID               a31UBW-2SN6-CXFk-qLOZ-qrsQ-BIYo-nZexXo

if you can see that you have no more FREE PE you are the king of raid. But you can see also with the command

[root@smeraid5 ~]# lvdisplay