Storage appliance with containers using Linux and ZFS

I'm working on Linux version of Sun storage machines, using commodity hardware, OpenVZ and Fuse-ZFS. I'm do have working system in my Sysadmin Cookbook so I might as well write a little bit of documentation about it.

My basic requirements are:

• Daily snapshots created with rsync on LVM snapshot from remote machines
• Snapshots are writable (using zfs clone) and can be converted back into running OpenVZ container (backuped machines are OpenVZ containers) for quick recovery or inspection of previous versions
• since disk space is limited (to 200Gb zfs mirror in my case) so I implemented snapshot expiatory

This makes it self-running system which won't fall over itself, so let's see how does it look:

root@opl:~# zpool status
  pool: opl
 state: ONLINE
 scrub: resilver completed after 1h59m with 0 errors on Wed Jun  3 15:29:50 2009
config:

        NAME        STATE     READ WRITE CKSUM
        opl         ONLINE       0     0     0
          mirror    ONLINE       0     0     0
            sda2    ONLINE       0     0     0
            sdb2    ONLINE       0     0     0

errors: No known data errors
root@opl:~# zfs list
NAME                           USED  AVAIL  REFER  MOUNTPOINT
opl                            183G  35.7G    21K  /opl
opl/backup                     180G  35.7G    22K  /opl/backup
opl/backup/212052             76.1G  35.7G  8.12G  /opl/backup/212052
opl/backup/212052@2009-05-01  5.69G      -  7.50G  -
opl/backup/212052@2009-05-10  5.69G      -  7.67G  -
opl/backup/212052@2009-05-15  5.57G      -  7.49G  -
opl/backup/212052@2009-05-22  3.54G      -  7.74G  -
opl/backup/212052@2009-05-25  3.99G      -  8.38G  -
opl/backup/212052@2009-05-26  3.99G      -  8.38G  -
...
opl/backup/212052@2009-06-05  3.72G      -  8.09G  -
opl/backup/212052@2009-06-06      0      -  8.12G  -
opl/backup/212056             1.42G  35.7G   674M  /opl/backup/212056
opl/backup/212056@2009-05-30  37.1M      -   688M  -
opl/backup/212056@2009-05-31  47.3M      -   747M  -
opl/backup/212056@2009-06-01  40.9M      -   762M  -
opl/backup/212056@2009-06-02  62.4M      -   787M  -
...
opl/backup/212056@2009-06-05  12.1M      -  1.02G  -
opl/backup/212056@2009-06-06      0      -   674M  -
opl/backup/212226              103G  35.7G  26.8G  /opl/backup/212226
opl/backup/212226@2009-05-05  4.29G      -  26.7G  -
opl/backup/212226@2009-05-10  4.04G      -  26.6G  -
opl/backup/212226@2009-05-15  4.19G      -  26.6G  -
opl/backup/212226@2009-05-22  4.12G      -  26.7G  -
opl/backup/212226@2009-05-23  4.12G      -  26.7G  -
opl/backup/212226@2009-05-24  4.09G      -  26.6G  -
opl/backup/212226@2009-05-25  4.14G      -  26.7G  -
opl/backup/212226@2009-05-26  4.13G      -  26.7G  -
...
opl/backup/212226@2009-06-05  4.20G      -  26.8G  -
opl/backup/212226@2009-06-06      0      -  26.8G  -
opl/clone                      719M  35.7G    25K  /opl/clone
opl/clone/212056-60018         666M  35.7G  1.39G  /opl/clone/212056-60018
opl/clone/212226-60017        53.0M  35.7G  26.7G  /opl/clone/212226-60017
opl/vz                        1.59G  35.7G  43.5K  /opl/vz
opl/vz/private                1.59G  35.7G    22K  /opl/vz/private
opl/vz/private/60014           869M  35.7G   869M  /opl/vz/private/60014
opl/vz/private/60015           488M  35.7G   488M  /opl/vz/private/60015
opl/vz/private/60016           275M  35.7G   275M  /opl/vz/private/60016

• pool is named same as machine (borrowing from Debian way of naming LVM volume groups) which makes it easy to export/import pools on different machines (I did run it with mirror over nbd for a while)
• snapshots names are dates of snapshot for easy overview
• clones (writable snapshots) are named using combination of backup and new container ID

There are several things which I wouldn't be able to get without zfs:

• clones can grows as much as they need
• data is compressed, which increase disk IO as result
• zfs and zpool commands are really nice and intuitive way to issue commands to filesystem
• zpool history is great idea of writing all filesystem operations to internal log
• ability to re-sliver (read/write all data on platters) together with checksums make it robust to disk errors