Ubuntu ZFS replication

April 20, 2016 admin

Most of you will know that Ubuntu 16.04 will have ZFS merged into the kernel. Despite licensing arguments I see this as a positive move. I recently tested btrfs replication (http://blog.ls-al.com/btrfs-replication/) but being a long time Solaris admin and understanding how easy ZFS makes things I welcome this development. Here is a quick test of ZFS replication between two Ubuntu 16.04 hosts.

Install zfs utils on both hosts.

# apt-get install zfsutils-linux

Quick and dirty create zpools using an image just for the test.

root@u1604b1-m1:~# dd if=/dev/zero of=/tank1.img bs=1G count=1 &> /dev/null
root@u1604b1-m1:~# zpool create tank1 /tank1.img 
root@u1604b1-m1:~# zpool list
NAME    SIZE  ALLOC   FREE  EXPANDSZ   FRAG    CAP  DEDUP  HEALTH  ALTROOT
tank1  1008M    50K  1008M         -     0%     0%  1.00x  ONLINE  -

root@u1604b1-m2:~# dd if=/dev/zero of=/tank1.img bs=1G count=1 &> /dev/null
root@u1604b1-m2:~# zpool create tank1 /tank1.img
root@u1604b1-m2:~# zpool list
NAME    SIZE  ALLOC   FREE  EXPANDSZ   FRAG    CAP  DEDUP  HEALTH  ALTROOT
tank1  1008M    64K  1008M         -     0%     0%  1.00x  ONLINE  -
root@u1604b1-m2:~# zfs list
NAME    USED  AVAIL  REFER  MOUNTPOINT
tank1    55K   976M    19K  /tank1

Copy a file into the source file system.

root@u1604b1-m1:~# cp /media/sf_E_DRIVE/W.pdf /tank1/
root@u1604b1-m1:~# ls -lh /tank1
total 12M
-rwxr-x--- 1 root root 12M Apr 20 19:22 W.pdf

Take a snapshot.

root@u1604b1-m1:~# zfs snapshot tank1@snapshot1
root@u1604b1-m1:~# zfs list -t snapshot
NAME              USED  AVAIL  REFER  MOUNTPOINT
tank1@snapshot1      0      -  11.2M  -

Verify empty target

root@u1604b1-m2:~# zfs list
NAME    USED  AVAIL  REFER  MOUNTPOINT
tank1    55K   976M    19K  /tank1

root@u1604b1-m2:~# zfs list -t snapshot
no datasets available

Send initial

root@u1604b1-m1:~# zfs send tank1@snapshot1 | ssh root@192.168.2.29 zfs recv tank1
root@192.168.2.29's password: 
cannot receive new filesystem stream: destination 'tank1' exists
must specify -F to overwrite it
warning: cannot send 'tank1@snapshot1': Broken pipe

root@u1604b1-m1:~# zfs send tank1@snapshot1 | ssh root@192.168.2.29 zfs recv -F tank1
root@192.168.2.29's password:

Check target.

root@u1604b1-m2:~# zfs list -t snapshot
NAME              USED  AVAIL  REFER  MOUNTPOINT
tank1@snapshot1      0      -  11.2M  -
root@u1604b1-m2:~# ls -lh /tank1
total 12M
-rwxr-x--- 1 root root 12M Apr 20 19:22 W.pdf

Lets populate one more file and take a new snapshot.

root@u1604b1-m1:~# cp /media/sf_E_DRIVE/S.pdf /tank1
root@u1604b1-m1:~# zfs snapshot tank1@snapshot2

Incremental send

root@u1604b1-m1:~# zfs send -i tank1@snapshot1 tank1@snapshot2 | ssh root@192.168.2.29 zfs recv tank1
root@192.168.2.29's password:

Check target

root@u1604b1-m2:~# ls -lh /tank1
total 12M
-rwxr-x--- 1 root root 375K Apr 20 19:27 S.pdf
-rwxr-x--- 1 root root  12M Apr 20 19:22 W.pdf

root@u1604b1-m2:~# zfs list -t snapshot
NAME              USED  AVAIL  REFER  MOUNTPOINT
tank1@snapshot1     9K      -  11.2M  -
tank1@snapshot2      0      -  11.5M  -