Expand ZFS Pool On Raw Disk Image

Introduction

I have a large raw disk image attached to a KVM virtual machine. It has run out of space, so I need to expand the disk. Normally I would just attach another disk and move the content to that larger disk, but that is not an option because the server does not have enough space to create yet another disk that is the same size or larger than the original. Thus, my only option is to expand the existing disk.

Steps

Create A Backup

If you can create a backup (probably by performing a ZFS send/recieve to another server), then go ahead and do that now.

Expand The Raw Disk

Run the following command to increase the size of your raw disk.

sudo qemu-img resize \
  -f raw \
  myDisk.raw \
  +[SIZE_IN_GB]G

You need to specify the additional amount, not the new total size. The disk needs to not be in use, so the easiest thing to do is turn off the virtual machine.

Identify Disk To Expand

Now we need to find out the name of the disk to expand (from within the server). I did this by running:

sudo zpool status -v

... which outputted the following:

  pool: zpool1
 state: ONLINE
config:

        NAME        STATE     READ WRITE CKSUM
        zpool1      ONLINE       0     0     0
          vdb       ONLINE       0     0     0

This shows that the disk that my pool is set up on is vdb.

Expand The Zpool

DISK="vdb"
sudo zpool online -e zpool1 $DISK

Now you should see that your pool has been expanded by running:

sudo zfs list

... which outputted for me:

NAME     USED  AVAIL     REFER  MOUNTPOINT
zpool1   147K  28.6G       24K  /zpool1

This should show you that you now have more available space in your pool.

References

• Serverfault - Increase the ZFS partition to use the entire disk