FreeNAS 0.7 and ZFS snapshots

Currently it is not possible to use the ZFS snapshot functionality via the Web-GUI. But you can use a script and cron to schedule snapshots.
You have to think about a schedule for the snapshots. I want to save my home-directories every hour (and have this snapshots available for 24 hours). Also I'd like to have a daily and a weekly snapshot (the daily snapshot will be available for 7 days the weeklys are stored for 4 weeks). All of the snapshots will be overwritten after that time.

First you need a place where you can store the script(s) that will create the snapshots.

I'm using a ZFS dataset called 'datapool/opt'. Under the directory 'bin' I'll have three scripts:

snapshot_hourly.sh
#!/bin/sh
zfs destroy $1@hourly.`date "+%H"` > /dev/null 2>&1
zfs snapshot $1@hourly.`date "+%H"`

snapshot_daily.sh
#!/bin/sh
zfs destroy $1@daily.`date "+%a"` > /dev/null 2>&1
zfs snapshot $1@daily.`date "+%a"`

snapshot_weekly.sh
#!/bin/sh
zfs destroy $1@weekly.4 > /dev/null 2>&1
zfs rename $1@weekly.3 @weekly.4 > /dev/null 2>&1
zfs rename $1@weekly.2 @weekly.3 > /dev/null 2>&1
zfs rename $1@weekly.1 @weekly.2 > /dev/null 2>&1
zfs snapshot $1@weekly.1

Be aware that these scripts should be executable!

freenas:/mnt/datapool/opt/bin# chmod 744 snapshot_*

Now you have to schedule the cron-jobs. You should do this via the Web-GUI. Go to -> System -> Advanced -> Cron

Command: /mnt/datapool/opt/bin/snapshot_hourly.sh datapool/home
User: root
Descritpion: Hourly snapshot of datapool/home
Schedule time:
minutes -> 0
hours -> All
days -> All
months -> All
week days -> All

Command: /mnt/datapool/opt/bin/snapshot_daily.sh datapool/home
User: root
Descritpion: Daily snapshot of datapool/home @ 20:00
Schedule time:
minutes -> 0
hours -> 20
days -> All
months -> All
week days -> All

Command: /mnt/datapool/opt/bin/snapshot_weekly.sh datapool/home
User: root
Descritpion: Weekly snapshot of datapool/home Sun @ 20:00
Schedule time:
minutes -> 0
hours -> 20
days -> All
months -> All
week days -> Sunday

After some time you will see somthing like this

freenas:~# zfs list
NAME USED AVAIL REFER MOUNTPOINT
...
datapool/home 14.9G 266G 21K /mnt/datapool/home
datapool/home@daily.Sat 0 - 21K -
datapool/home@weekly.2 0 - 21K -
datapool/home@daily.Fri 0 - 21K -
datapool/home@daily.Sun 0 - 21K -
datapool/home@weekly.1 0 - 21K -
datapool/home@daily.Mon 0 - 21K -
datapool/home@daily.Tue 0 - 21K -
datapool/home@daily.Wed 0 - 21K -
datapool/home@hourly.14 0 - 21K -
datapool/home@hourly.15 0 - 21K -
datapool/home@hourly.16 0 - 21K -
datapool/home@hourly.17 0 - 21K -
datapool/home@hourly.18 0 - 21K -
datapool/home@hourly.19 0 - 21K -
datapool/home@hourly.20 0 - 21K -
datapool/home@daily.Thu 0 - 21K -
datapool/home@hourly.21 0 - 21K -
datapool/home@hourly.22 0 - 21K -
datapool/home@hourly.23 0 - 21K -
datapool/home@hourly.00 0 - 21K -
datapool/home@hourly.01 0 - 21K -
datapool/home@hourly.02 0 - 21K -
datapool/home@hourly.03 0 - 21K -
datapool/home@hourly.04 0 - 21K -
datapool/home@hourly.05 0 - 21K -
datapool/home@hourly.06 0 - 21K -
datapool/home@hourly.07 0 - 21K -
datapool/home@hourly.08 0 - 21K -
datapool/home@hourly.09 0 - 21K -
datapool/home@hourly.10 0 - 21K -
datapool/home@hourly.11 0 - 21K -
datapool/home@hourly.12 0 - 21K -
datapool/home@hourly.13 0 - 21K -
...

How it works...

I've created a 10MB testfile

freenas:/mnt/datapool/home# dd if=/dev/zero of=testfile bs=1024k count=10
10+0 records in
10+0 records out
10485760 bytes transferred in 0.159408 secs (65779346 bytes/sec)
freenas:/mnt/datapool/home# ls -l
total 10237
-rw-r--r-- 1 root wheel 10485760 Aug 15 15:13 testfile
freenas:/mnt/datapool/home# df -h
Filesystem Size Used Avail Capacity Mounted on
...
datapool/home 5.3G 10M 5.3G 0% /mnt/datapool/home

Now there will be a snapshot created... (either via cron or the script -> freenas:/mnt/datapool/home# /mnt/datapool/opt/bin/snapshot_hourly.sh datapool/home)

freenas:/mnt/datapool/home# zfs list
NAME USED AVAIL REFER MOUNTPOINT
...
datapool/home 10.0M 5.34G 10.0M /mnt/datapool/home
datapool/home@hourly.15 0 - 10.0M -
...

If the file will be deleted...

freenas:/mnt/datapool/home# rm testfile
freenas:/mnt/datapool/home# zfs list
NAME USED AVAIL REFER MOUNTPOINT
...
datapool/home 10.0M 5.34G 26.9K /mnt/datapool/home
datapool/home@hourly.15 10.0M - 10.0M -

As you can see, the snapshot growed by 10MByte. But the file is gone...

freenas:/mnt/datapool/home# ls -al
total 4
drwxr-xr-x 2 root wheel 2 Aug 15 15:16 .
drwxrwxrwx 5 root wheel 5 Aug 15 13:58 ..

But how can I access the snapshot? Change to the .zfs/snapshot directory. And there you can see the snapshots.

freenas:/mnt/datapool/home# cd .zfs/snapshot
freenas:/mnt/datapool/home/.zfs/snapshot# ls
...
hourly.15
...

freenas:/mnt/datapool/home/.zfs/snapshot# cd hourly.15
freenas:/mnt/datapool/home/.zfs/snapshot/hourly.15# ls -l
total 10237
-rw-r--r-- 1 root wheel 10485760 Aug 15 15:13 testfile

Be aware! Snapshots are Read-Only. So you can copy this file back to the origin, or wherever you want.