Save Ukraine

Migrating a file server with zfs

Christian Kruse,

At the company I'm working for we have a central NAS. This NAS contains all user homes, backups and such. It is a small box with four HDDs running a FreeBSD on a ZFS RAID-Z2. Recently we switched to newer hardware. Transferring the data traditionally takes 13 hours - a big time frame. I can't shut down the server for 13 hours, working hours are from 07:00 o'clock to 21:00 o'clock. Gladly we use ZFS! I created a snapshot and sent it to the new server:

zfs snapshot zroot/var/storage@base
zfs send zroot/var/storage@base | ssh zfs receive zroot/var/storage

This took round about 13 hours. But during that time the users could work normally, due to the snapshot the changes did not interfere with the zfs send. When it was finished I waited until 21:00, created another snapshot and sent only the difference to the new server:

zfs snapshot zroot/var/storage@latest
zfs send -i base zroot/var/storage@latest | ssh zfs receive -F zroot/var/storage

After that I shut down the old server, set the IP on the new server to the IP of the old one and voila - everything works as expected! The actual switch took me just 10 minutes.

ZFS really rocks :)