Schlagwort-Archive: LVM

Add a new disk to RAID array and enlarge LVM and ext4 file system

Inside my home server were three hard drives combined to a RAID 5. On this large volume I then created three logic volumes1 with the LVM (Logic Volume Manager). As time went by, space was running out on the large storage volume, so I bought a new hard drive. Here are the steps required, maybe it helps others (and a future myself), who want to do the same.

Note: All commands are supposed to be run as a super user. So either log into root or use sudo.
Another Note: Everything is done online with the file system mounted, but it is slower than having it not mounted.

Add hard drive to RAID

First add the hard drive to the RAID and let it reshape. For my 3 TB disk the reshaping took roughly two days, so be patient. In runs in the background, though.

$ mdadm --add /dev/md0 /dev/sde1
$ mdadm --grow --raid-devices=4 /dev/md0

You can check the progress with mdadm --detail /dev/md0:

    Update Time : Sun Jun 23 21:35:02 2013
          State : clean, reshaping 
 Active Devices : 4
Working Devices : 4
 Failed Devices : 0
  Spare Devices : 0

         Layout : left-symmetric
     Chunk Size : 512K

 Reshape Status : 56% complete
  Delta Devices : 1, (3->4)

A step I forgot at first and lead to errors during booting: adding the new hard disk to the RAID configuration file. Open the file /etc/mdadm/mdadm.conf with an editor of your choice.

# mdadm.conf
# Please refer to mdadm.conf(5) for information about this file.

# by default (built-in), scan all partitions (/proc/partitions) and all
# containers for MD superblocks. alternatively, specify devices to scan, using
# wildcards if desired.
#DEVICE partitions containers
DEVICE /dev/sd[bcd]1


In line 10 add the new disk (sde1):

DEVICE /dev/sd[bcde]1

Now it should also work after rebooting.

Enlarge the physical volume on the RAID

We now have a larger virtual hard drive on the RAID array. Instead of just applying a filesystem to that, I first added another layer of structure, the LVM. So we have to tell the physical volume (comparable to a hard drive) that more space is available now (pvresize).

$ pvs
  PV         VG   Fmt  Attr PSize PFree
  /dev/md0   raid lvm2 a-   5.46t    0 
$ pvresize -v /dev/md0 
    Using physical volume(s) on command line
    Archiving volume group "raid" metadata (seqno 6).
    Resizing physical volume /dev/md0 from 1430729 to 2146094 extents.
    Resizing volume "/dev/md0" to 17580802048 sectors.
    Updating physical volume "/dev/md0"
    Creating volume group backup "/etc/lvm/backup/raid" (seqno 7).
  Physical volume "/dev/md0" changed
  1 physical volume(s) resized / 0 physical volume(s) not resized
$ pvs
  PV         VG   Fmt  Attr PSize PFree
  /dev/md0   raid lvm2 a-   8.19t 2.73t

Enlarge the logical volume

Now the LVM nows that more space is available (like having a larger hard disk). The next step is to enlarge the partition on this hard drive, the logical volume. The procedure is pretty much the same:

$ lvs
  LV            VG   Attr   LSize   Origin Snap%  Move Log Copy%  Convert
  backup_user1  raid -wi-ao 500.00g                                      
  backup_user2  raid -wi-ao 250.00g                                      
  storage       raid -wi-ao   4.73t                                      
$ lvresize --extents +100%FREE /dev/raid/storage
  Extending logical volume storage to 7.45 TiB
  Logical volume storage successfully resized
$ lvs
  LV            VG   Attr   LSize   Origin Snap%  Move Log Copy%  Convert
  backup_user1  raid -wi-ao 500.00g                                      
  backup_user2  raid -wi-ao 250.00g                                      
  storage       raid -wi-ao   7.45t                                      

Enlarge the file system

Last part in the Inception-like volume chain: the file system (ext4 in my case). Resizing it takes a while (similar to the growing of the RAID), but it doesn’t run in the background. So if you are not working on the PC directly, use a screen session2.

$ df -h | grep storage
  /dev/mapper/raid-storage        4.7T  4.6T  118G  98% /srv/storage
$ resize2fs /dev/raid/storage
$ df -h | grep storage
  /dev/mapper/raid-storage        7,4T    4,6T  2,9T   62% /srv/storage

After doing this you should check the file system for errors. I believe this is asked after the resize process, unfortunately I forgot to look and just powered off the PC. To initiate a check manually, you call fsck.ext4 -pf /dev/mapper/raid-storage

  1. One large storage volume and two separate backup volumes. []
  2. I first forgot this, but aborting the resize doesn’t seem to have any effect on the data. []