Date: Sat, 19 Jan 2019 15:08:29 -0500 From: Rich <rincebrain@gmail.com> To: Maciej Jan Broniarz <gausus@gausus.net> Cc: freebsd-fs <freebsd-fs@freebsd.org> Subject: Re: ZFS on Hardware RAID Message-ID: <CAOeNLurgn-ep1e=Lq9kgxXK%2By5xqq4ULnudKZAbye59Ys7q96Q@mail.gmail.com> In-Reply-To: <92646202.63422.1547910433715.JavaMail.zimbra@gausus.net> References: <1180280695.63420.1547910313494.JavaMail.zimbra@gausus.net> <92646202.63422.1547910433715.JavaMail.zimbra@gausus.net>
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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@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@freebsd.org mailing list > https://lists.freebsd.org/mailman/listinfo/freebsd-fs > To unsubscribe, send any mail to "freebsd-fs-unsubscribe@freebsd.org"
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