Hi all,

Currently running a 4x16TB ZFS RAIDZ1 pool on a machine that could handle much more.

I’m thinking about expanding storage. My original plan was to add 1-4 drives and eventually move to RAIDZ2 / dual parity.

From what I understand, you can grow an existing RAIDZ1, but cannot later convert it into RAIDZ2. Is that correct?

So what would you consider the smarter approach, especially now in light of the insane prices for storage?

• 1) Expand the existing RAIDZ1 gradually? Like 1 drive at a time. (if so, how many drives would you risk to keep in RAIDZ1?)

• 2) Rebuild/migrate into a fresh RAIDZ2 pool? (If so, where do you park your stuff during migration? I could temporary expand a cloud storage. Is that already the answer to my question? ;) )

• 3) Or any other idea?

Thanks for any advice. :) And sorry if this has been asked a million times before.

11 hours ago, stahlblau said:

but cannot later convert it into RAIDZ2. Is that correct?

Correct.

11 hours ago, stahlblau said:

Expand the existing RAIDZ1 gradually? Like 1 drive at a time. (if so, how many drives would you risk to keep in RAIDZ1?)

It also depends on the size of drives, but typically up to around 8 drives can be OK with raidz1

Thanks @JorgeB - drives are 16TB each (Seagate Ironwolf Pro). Would you rather add drives gradually as more space is needed, or go straight to a larger RAIDZ2 setup?

I’ve read that RAIDZ expansion puts quite a bit of IO stress on all drives, so I’m wondering whether doing a bigger migration upfront might actually be better for drive-health. Or is the additional IO load during RAIDZ expansion basically negligible in terms of overall drive health, if it only happens every 3 months or so?

For some additional context: with my current storage growth, adding just a single drive would probably buy me around 3 more months before needing another expansion. Adding 4-6 drives instead would likely give me much more breathing room and possibly avoid another expansion entirely for the next few years.

It would mostly depend on how good the backups are. The extra I/O should not be a big deal for healthy drives.

Thanks again. Last question: what do you mean by "good backups"? Backups of the NAS content, in case of drive failure and raidz1 cannot solve it, cause raidz2 or more would have been needed?

You should have backups of anything important either way, if you have good backups and they are easy to restore, RAIDZ1 is less of a risk, but even with RAIDZ2, backups are still needed.

Absolutely. I just wanted to clarify what you mean by “good backups" in that case. Thank you Jorge!