Gradual Disk Replacement in RAIDZ1: Expanding Capacity from 2TB to 4TB

TrueNAS General
1

I currently have a RAIDZ1 array with three 1TB disks, giving me a total capacity of 2TB. Can I gradually replace each 1TB disk with a 2TB disk one by one, and after replacing all three disks, execute an expand operation to increase the total capacity to 4TB?

2

Yes. ZFS should even expand automatically without manual intervention.

If possible, do not physically remove the old drives until the replacement is complete. Plug in a new drive, replece an existing drive from the GUI, wait and the remove the drive which had been replaced (check serial number!). Rince and repeat.

3 Likes
3

ZFS has a zpool property to control auto expanding pools. TrueNAS sets it to on for non-boot pools and off for the boot-pool. So non-boot pools should auto-expand as soon as the space is available, while boot-pool should not.

admin@KrausHaus[~]$ /sbin/zpool get autoexpand   
NAME       PROPERTY    VALUE   SOURCE
KH         autoexpand  on      local
VMs        autoexpand  on      local
boot-pool  autoexpand  off     default
admin@KrausHaus[~]$
4

This depends on a bunch of factors beyond just the autoexpand property.

So, if it doesn’t auto expand, then there is a button on the pool “expand” which should do the trick

5

Besides disk capacity and autoexpand property, what else does automatic expansion depend on?

6

One example is the size of the partition, and how different versions of TrueNAS have handled that differently.