Hi

I have purchased a mechanical SATA HDD, in the UK we seem to be having a bit of a HDD shortage.

So I will be get a second with a pre-order; though SCAN have told me Seagate have a backorder on the EXOS.

I want to set up a RAID 1 style cache.

However I am only going to have the one drive for now.

I think with two drives - I'd like ZFS RAIDZ1.

I intend to store vdisks on it and iso's - whilst keeping my system cache (NVME) for dockers and apps. So speed + 1disk failure redundancy is what I want is the goal.

I realise this is non-conventional to know you want mirroring but have only one disk - but I want to start using it asap as a cache pool. Then take large vdisks off my array and into a cache pool.

I know ButterFS is good for flexibility.

My question is -

(1) What initial file system should I use?

(2) If I can use ZFS can i then install a second of the same size; and select RAIDZ1?

Thanks

Chris

Edited December 5, 2025Dec 5 by SmokeyColes

5 minutes ago, SmokeyColes said:

I think with two drives - I'd like ZFS RAIDZ1.

Unless you plan to expand that in the future, I recommend creating a ZFS mirror instead

Also note that you can add a device to a single ZFS pool to create a mirror, but not add one to create a 2-device RAIDZ1; for that you would need to recreate the pool.

@JorgeB - could you help explain; how can a single drive create a mirror.

Can you create two ZFS pools independently; where one mirrors the other? Or is it a case of adding a drive in that pool with a setting for mirror?

1 minute ago, JorgeB said:

Also note that you can add a device to a single ZFS pool to create a mirror, but not add one to create a 2-device RAIDZ1; for that you would need to recreate the pool.

Just now, SmokeyColes said:

could you help explain; how can a single drive create a mirror.

You start with a single drive, then add another one to make a mirror.

@JorgeB perfect

That's what I will do.