Grow a GFS2 Partition

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 AN!Wiki :: How To :: Grow a GFS2 Partition

This is a brief tutorial on growing a GFS2 partition that exists on an LVM LV backed by a DRBD resource in a Two Node Fedora 13 Cluster.

Growing a GFS2 Partition

To grow a GFS2 partition, you must know where it is mounted. You can not grow an unmounted GFS2 partition, as odd as that may seem at first. Also, you only need to run grow commands from one node. Once completed, all nodes will see and use the new free space automatically.

This requires two steps to complete:

  1. Extend the underlying LVM logical volume
  2. Grow the actual GFS2 partition

Extend the LVM LV

To keep things simple, we'll just use some of the free space we left on our /dev/drbd0 LVM physical volume. If you need to add more storage to your LVM first, please follow the instructions in the article: "Adding Space to an LVM" before proceeding.

Let's add 50GB to our GFS2 logical volume /dev/drbd_vg0/xen_store from the /dev/drbd0 physical volume, which we know is available because we left more than that back when we first setup our LVM. To actually add the space, we need to use the lvextend command:

lvextend -L +50G /dev/drbd_vg0/xen_store /dev/drbd0

Which should return:

  Extending logical volume xen_store to 70.00 GB
  Logical volume xen_store successfully resized

If we run lvdisplay /dev/drbd_vg0/xen_store now, we should see the extra space.

  --- Logical volume ---
  LV Name                /dev/drbd_vg0/xen_store
  VG Name                drbd_vg0
  LV UUID                svJx35-KDXK-ojD2-UDAA-Ah9t-UgUl-ijekhf
  LV Write Access        read/write
  LV Status              available
  # open                 1
  LV Size                70.00 GB
  Current LE             17920
  Segments               2
  Allocation             inherit
  Read ahead sectors     auto
  - currently set to     256
  Block device           253:3

You're now ready to proceed.

Grow The GFS2 Partition

This step is pretty simple, but you need to enter the commands exactly. Also, you'll want to do a dry-run first and address any resulting errors before issuing the final gfs2_grow command.

To get the exact name to use when calling gfs2_grow, run the following command:

gfs2_tool df
  SB lock proto = "lock_dlm"
  SB lock table = "an-cluster:xen_store"
  SB ondisk format = 1801
  SB multihost format = 1900
  Block size = 4096
  Journals = 2
  Resource Groups = 80
  Mounted lock proto = "lock_dlm"
  Mounted lock table = "an-cluster:xen_store"
  Mounted host data = "jid=1:id=196610:first=0"
  Journal number = 1
  Lock module flags = 0
  Local flocks = FALSE
  Local caching = FALSE
  Type           Total Blocks   Used Blocks    Free Blocks    use%           
  data           5242304        1773818        3468486        34%
  inodes         3468580        94             3468486        0%

From this output, we know that GFS2 expects the name "/xen_store". Even adding something as simple as a trailing slash will not work. The program we will use is called gfs2_grow with the -T switch to run the command as a test to work out possible errors.

For example, if you added the trailing slash, this is the kind of error you would see:

Bad command:

gfs2_grow -T /xen_store/
GFS Filesystem /xen_store/ not found

Once we get it right, it will look like this:

gfs2_grow -T /xen_store
(Test mode--File system will not be changed)
FS: Mount Point: /xen_store
FS: Device:      /dev/mapper/drbd_vg0-xen_store
FS: Size:        5242878 (0x4ffffe)
FS: RG size:     65535 (0xffff)
DEV: Size:       18350080 (0x1180000)
The file system grew by 51200MB.
gfs2_grow complete.

This looks good! We're now ready to re-run the command without the -T switch:

gfs2_grow /xen_store
FS: Mount Point: /xen_store
FS: Device:      /dev/mapper/drbd_vg0-xen_store
FS: Size:        5242878 (0x4ffffe)
FS: RG size:     65535 (0xffff)
DEV: Size:       18350080 (0x1180000)
The file system grew by 51200MB.
gfs2_grow complete.

You can check that the new space is available on both nodes now using a simple call like df -h.


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