Date: Sat, 19 Jan 2019 15:15:05 -0500 From: Ira Cooper <ira@wakeful.net> To: Rich <rincebrain@gmail.com> Cc: Maciej Jan Broniarz <gausus@gausus.net>, freebsd-fs <freebsd-fs@freebsd.org> Subject: Re: ZFS on Hardware RAID Message-ID: <CAAPGDwJTcRkwz=e%2BC0bn1A=-nu9P=aOQuB=CWg%2BivdbgPfviRA@mail.gmail.com> In-Reply-To: <CAOeNLurgn-ep1e=Lq9kgxXK%2By5xqq4ULnudKZAbye59Ys7q96Q@mail.gmail.com> References: <1180280695.63420.1547910313494.JavaMail.zimbra@gausus.net> <92646202.63422.1547910433715.JavaMail.zimbra@gausus.net> <CAOeNLurgn-ep1e=Lq9kgxXK%2By5xqq4ULnudKZAbye59Ys7q96Q@mail.gmail.com>
next in thread | previous in thread | raw e-mail | index | archive | help
Well put. In addition, by using a raid controller, you are likely depriving the OS and ZFS the ability to use the drive's writeback caches, and queue depth management. Cheers, -Ira On Sat, Jan 19, 2019 at 3:09 PM Rich <rincebrain@gmail.com> wrote: > 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" > _______________________________________________ > 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" >
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?CAAPGDwJTcRkwz=e%2BC0bn1A=-nu9P=aOQuB=CWg%2BivdbgPfviRA>