ZFS mirror anyone?


has anyone tried making a ZFS mirror (RAID1 equivalent) on the laptop? I’d be interested in either M2 and expansion card and 2+ expansion cards mirrors (/ RAIDZ).

I’m mostly concerned about latency, since USB doesn’t have exactly stellar reputation in that department. So… if anyone here tried mirroring the root partition I’d love to hear how it works in practice and see some bench results :smiley:

Does the whole idea sound sensible without a second m2 slot?

Probably not a good idea, I’d say you’d probably either have it not work, or it will cripple the performance of the M.2 Drive. Also a PS, I don’t see why you’d need to mirror drives for a laptop. If it’s for loosing data then you should probably invest in ensuring everything gets properly backed up using a tool like ansible or manually backing up files.

It’ll definitely throttle down the write performance of the M.2 drive to that of the expansion card. I’m interested how in usable would the resulting storage be for a daily driver laptop (I’m aware that’s a quite vague workload description) due to USB latency. It’ll definitely be worse than 2xM.2, but maybe good enough.

As for the mirrors: my RPO for a single drive failure is somewhere around a single block. Given a single disk, total fault of the system is a certain event at some point unless you plan on swapping that single drive while it still works (which doesn’t give you certainty and generates waste). There is a few orders of magnitude smaller possibility of 2 drives failing before I replace the 1st faulty one and perform full resilvering. In that (unlikely) case I’m happy with RPO of 24h, which is how often I do my backups to external storage.

I can absolutely imagine someone having a different value for those RPO parameters, in which case a single drive + backup might suffice.