ZFS on Hardware RAID

[Rich]

The two caveats I'd offer are:
- RAID controllers add an opaque complexity layer if you have problems
- e.g. if you're using single-disk RAID0s to make a RAID controller
pretend to be an HBA, if the disk starts misbehaving, you have an
additional layer of behavior (how the RAID controller interprets
drives misbehaving and shows that to the OS) to figure out whether the
drive is bad, the connection is loose, the controller is bad, ...
- abstracting the redundancy away from ZFS means that ZFS can't
recover if it knows there's a problem but the underlying RAID
controller doesn't - that is, say you made a RAID-6, and ZFS sees some
block fail checksum. There's not a way to say "hey that block was
wrong, try that read again with different disks" to the controller, so
you're just sad at data loss on your nominally "redundant" array.

- Rich

On Sat, Jan 19, 2019 at 11:44 AM Maciej Jan Broniarz <gausus at gausus.net> wrote:
>
> Hi,
>
> I want to use ZFS on a hardware-raid array. I have no option of making it JBOD. I know it is best to use ZFS on JBOD, but
> that possible in that particular case. My question is - how bad of an idea is it. I have read very different opinions on that subject, but none of them seems conclusive.
>
> Any comments and especially case studies are most welcome.
> All best,
> mjb
> _______________________________________________
> freebsd-fs at freebsd.org mailing list
> https://lists.freebsd.org/mailman/listinfo/freebsd-fs
> To unsubscribe, send any mail to "freebsd-fs-unsubscribe at freebsd.org"