Hi all!
I’m in the process of migrating my home server from Unraid to TrueNAS with a ZFS pool, as well as upping storage from 2 6TB drives to 4. Unfortunately, because of either my bad luck or incompetence, it seems like one of the drives has died. So, here’s my question. I’ve read up a bit on resilvering and I know that if I replace the dead drive with a larger drive, the pool will be unable to use that extra space until the remaining drives are upgraded, but would there be any other drawbacks? Especially if the pool was left running in this configuration for an extended period.
I definitely see myself upgrading the pool to larger drives in the future, and it would be nice to save myself buying an extra drive that may end up getting replaced before the end of its life. (Note: I’m aware that resilvering isn’t the safest way of upgrading a pool, but the data on the pool is either backed up or non-essential, so I’m fine with the risks)
I run my Truenas Scale with 5 mirror vdevs. This is sort of like raid 10 (I don’t need the differences explained to me). This means that I get 50% of the raw storage as usable but, it means that to upgrade space, I only need to upgrade two drives at a time. It also means that replacing a failed drive is fast, much faster than replacing a drive from a raidz* vdev. As you move to Truenas, this is something to consider. Given that you’re going to have 4 drives total, I don’t think you’d be wasting any additional space as you shouldn’t consider raidz safe (same problem as raid 5, high risk of second drive failure during rebuild) which leaves you at raidz2.