ZFS on Hardware RAID

[Ira Cooper]

On Sat, Jan 19, 2019 at 11:43 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,
>

I've actually built Illumos based ZFS NAS systems based on raid controllers
and non-raid controllers.

If given the choice, I'd use non-raid controllers, today.  (HBAs)

Why?  Because ZFS handles the "raid" layer well.  The write back cache a
RAID controller provides, isn't really needed with ZIL, nor desired.

All a raid controller really brings in my experience is added operational
complexity once you use good enough hardware, mainly good ZIL drives and
HBAs.

So it isn't really a "bad" idea, more just redundant, expensive and
inconvenient.  You could have good reasons to do it, like that the RAID
controller is built into the motherboard etc.

Just make sure your data integrity is #1.  Writeback caches are properly
battery protected, or not used. etc.

Best,

-Ira