Date: Sun, 20 Jan 2019 08:45:21 +0000 (GMT) From: andy thomas <andy@time-domain.co.uk> 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: <alpine.BSF.2.21.1901200834470.12592@mail0.time-domain.co.uk> 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>
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I have to agree with your comment that hardware RAID controllers add another layer of opaque complexity but for what it's worth, I have to admit ZFS on h/w RAID does work and can work well in practice. I run a number of very busy webservers (Dell PowerEdge 2950 with LSI MegaRAID SAS 1078 controllers) with the first two disks in RAID 1 as the FreeBSD system disk and the remaining 4 disks configured as RAID 0 virtual disks making up a ZFS RAIDz1 pool with 3 disks plus one hot spare. With 6-10 jails running on each server, these have been running for years with no problems at all. Andy On Sat, 19 Jan 2019, Rich 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" > ---------------------------- Andy Thomas, Time Domain Systems Tel: +44 (0)7866 556626 Fax: +44 (0)20 8372 2582 http://www.time-domain.co.uk
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