From the Canyon Edge -- :-Dustin

Tuesday, February 16, 2016

ZFS is *the* FS for Containers in Ubuntu 16.04!

Ubuntu 16.04 LTS (Xenial) is only a few short weeks away, and with it comes one of the most exciting new features Linux has seen in a very long time...

ZFS -- baked directly into Ubuntu -- supported by Canonical.

What is ZFS?

ZFS is a combination of a volume manager (like LVM) and a filesystem (like ext4, xfs, or btrfs).

ZFS one of the most beloved features of Solaris, universally coveted by every Linux sysadmin with a Solaris background.  To our delight, we're happy to make to OpenZFS available on every Ubuntu system.  Ubuntu's reference guide for ZFS can be found here, and these are a few of the killer features:
  • snapshots
  • copy-on-write cloning
  • continuous integrity checking against data corruption
  • automatic repair
  • efficient data compression.
These features truly make ZFS the perfect filesystem for containers.

What does "support" mean?

  • You'll find zfs.ko automatically built and installed on your Ubuntu systems.  No more DKMS-built modules!
$ locate zfs.ko
  • You'll see the module loaded automatically if you use it.

$ lsmod | grep zfs
zfs                  2801664  11
zunicode              331776  1 zfs
zcommon                57344  1 zfs
znvpair                90112  2 zfs,zcommon
spl                   102400  3 zfs,zcommon,znvpair
zavl                   16384  1 zfs

  • The user space zfsutils-linux package will be included in Ubuntu Main, with security updates provided by Canonical (as soon as this MIR is completed).
  • As always, industry leading, enterprise class technical support is available from Canonical with Ubuntu Advantage services.

How do I get started?

It's really quite simple!  Here's a few commands to get you up and running with ZFS and LXD in 60 seconds or less.

First, make sure you're running Ubuntu 16.04 (Xenial).

$ head -n1 /etc/issue
Ubuntu Xenial Xerus (development branch) \n \l

Now, let's install lxd and zfsutils-linux, if you haven't already:

$ sudo apt install lxd zfsutils-linux

Next, let's use the interactive lxd init command to setup LXD and ZFS.  In the example below, I'm simply using a sparse, loopback file for the ZFS pool.  For best results (and what I use on my laptop and production servers), it's best to use a raw SSD partition or device.

$ sudo lxd init
Name of the storage backend to use (dir or zfs): zfs
Create a new ZFS pool (yes/no)? yes
Name of the new ZFS pool: lxd
Would you like to use an existing block device (yes/no)? no
Size in GB of the new loop device (1GB minimum): 2
Would you like LXD to be available over the network (yes/no)? no 
LXD has been successfully configured.

We can check our ZFS pool now:

$ sudo zpool list
lxd   1.98G   450K  1.98G         -     0%     0%  1.00x  ONLINE  -

$ sudo zpool status
  pool: lxd
 state: ONLINE
  scan: none requested

        NAME                    STATE     READ WRITE CKSUM
        lxd                     ONLINE       0     0     0
          /var/lib/lxd/zfs.img  ONLINE       0     0     0
errors: No known data errors

$ lxc config get storage.zfs_pool_name
storage.zfs_pool_name: lxd

Finally, let's import the Ubuntu LXD image, and launch a few containers.  Note how fast containers launch, which is enabled by the ZFS cloning and copy-on-write features:

$ newgrp lxd
$ lxd-images import ubuntu --alias ubuntu
Downloading the GPG key for
Progress: 48 %
Validating the GPG signature of /tmp/tmpa71cw5wl/download.json.asc
Downloading the image.
Image manifest:
Image imported as: 54c8caac1f61901ed86c68f24af5f5d3672bdc62c71d04f06df3a59e95684473
Setup alias: ubuntu

$ for i in $(seq 1 5); do lxc launch ubuntu; done
$ lxc list
|          NAME           |  STATE  |       IPV4        | IPV6 | EPHEMERAL | SNAPSHOTS |
| discordant-loria        | RUNNING | (eth0) |      | NO        |         0 |
| fictive-noble           | RUNNING | (eth0)  |      | NO        |         0 |
| interprotoplasmic-essie | RUNNING | (eth0) |      | NO        |         0 |
| nondamaging-cain        | RUNNING | (eth0)   |      | NO        |         0 |
| untreasurable-efrain    | RUNNING | (eth0)  |      | NO        |         0 |

Super easy, right?