Date: Sun, 20 Jan 2019 22:34:31 -0800 From: Xin Li <delphij@delphij.net> To: freebsd-fs@freebsd.org Subject: Re: ZFS on Hardware RAID Message-ID: <7e496a87-9c94-63e7-e48e-7f719c2e7874@delphij.net> In-Reply-To: <1691666278.63816.1547976245836.JavaMail.zimbra@gausus.net> References: <1180280695.63420.1547910313494.JavaMail.zimbra@gausus.net> <92646202.63422.1547910433715.JavaMail.zimbra@gausus.net> <CAOeNLurgn-ep1e=Lq9kgxXK%2By5xqq4ULnudKZAbye59Ys7q96Q@mail.gmail.com> <alpine.BSF.2.21.1901200834470.12592@mail0.time-domain.co.uk> <1691666278.63816.1547976245836.JavaMail.zimbra@gausus.net>
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This is an OpenPGP/MIME signed message (RFC 4880 and 3156) --ZgN8q2zxDFUkdMnT3BGlRx1UpT5ovRvhq Content-Type: multipart/mixed; boundary="Ff9DMMrcplC0uSkPEXxyawPmsOV379354"; protected-headers="v1" From: Xin Li <delphij@delphij.net> Reply-To: d@delphij.net To: freebsd-fs@freebsd.org Message-ID: <7e496a87-9c94-63e7-e48e-7f719c2e7874@delphij.net> Subject: Re: ZFS on Hardware RAID References: <1180280695.63420.1547910313494.JavaMail.zimbra@gausus.net> <92646202.63422.1547910433715.JavaMail.zimbra@gausus.net> <CAOeNLurgn-ep1e=Lq9kgxXK+y5xqq4ULnudKZAbye59Ys7q96Q@mail.gmail.com> <alpine.BSF.2.21.1901200834470.12592@mail0.time-domain.co.uk> <1691666278.63816.1547976245836.JavaMail.zimbra@gausus.net> In-Reply-To: <1691666278.63816.1547976245836.JavaMail.zimbra@gausus.net> --Ff9DMMrcplC0uSkPEXxyawPmsOV379354 Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: quoted-printable On 1/20/19 01:24, Maciej Jan Broniarz wrote: > Hi, >=20 > I am thinking about the scenario with ZFS on single disks configured to= RAID0 by hw raid. > Please correct me, if i'm wrong, but HW Raid uses a dedicated unit to p= rocess all RAID related work (eg. parity checks). > With ZFS the job is done by CPU. How significant is the performance los= s in that particular case? But you don't really skip that cost when layering ZFS on top of a hardware RAID. ZFS still does checksumming, etc., and you really want it to do its job because a) it would tell you which files were corrupted in the worst case scenario, and b) when doing scrubs, ZFS only scans areas with data, while in hardware RAID case, the filesystem is opaque and it has to scan everything. >=20 > mjb >=20 >=20 > ----- Oryginalna wiadomo=C5=9B=C4=87 ----- > Od: "andy thomas" <andy@time-domain.co.uk> > Do: "Rich" <rincebrain@gmail.com> > DW: "Maciej Jan Broniarz" <gausus@gausus.net>, "freebsd-fs" <freebsd-fs= @freebsd.org> > Wys=C5=82ane: niedziela, 20 stycze=C5=84 2019 9:45:21 > Temat: Re: ZFS on Hardware RAID >=20 > I have to agree with your comment that hardware RAID controllers add=20 > another layer of opaque complexity but for what it's worth, I have to=20 > admit ZFS on h/w RAID does work and can work well in practice. >=20 > I run a number of very busy webservers (Dell PowerEdge 2950 with LSI=20 > MegaRAID SAS 1078 controllers) with the first two disks in RAID 1 as th= e=20 > FreeBSD system disk and the remaining 4 disks configured as RAID 0 virt= ual=20 > disks making up a ZFS RAIDz1 pool with 3 disks plus one hot spare.=20 > With 6-10 jails running on each server, these have been running for=20 > years with no problems at all. >=20 > Andy >=20 > On Sat, 19 Jan 2019, Rich wrote: >=20 >> 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.ne= t> wrote: >>> >>> Hi, >>> >>> I want to use ZFS on a hardware-raid array. I have no option of makin= g 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 non= e 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" >> >=20 >=20 > ---------------------------- > Andy Thomas, > Time Domain Systems >=20 > Tel: +44 (0)7866 556626 > Fax: +44 (0)20 8372 2582 > http://www.time-domain.co.uk > _______________________________________________ > 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" >=20 --Ff9DMMrcplC0uSkPEXxyawPmsOV379354-- --ZgN8q2zxDFUkdMnT3BGlRx1UpT5ovRvhq Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- iQIcBAEBCgAGBQJcRWf7AAoJEEB5f3yV9INPj24P/R3MJYhg1QG9hydGuqitIWWZ nhK8zPfZ09YAt/PnHr7VWP6zMIPsLMP1NHYxmJd2erC2GdsI7GOM9ZgNBz+zb/u4 uYQdbZz3ObFVQIayGoHpuxTxJnpPXmjj4LkwoVPY/5SIcGplGvEDNBVn1aPDWbwl PXu9IMjekgQ4Ih4a4X2o5Vb3CY51FuIVNNzr+G5AM6kA47bXjSwO4SDHeFUJvwsu f44XZECeaa2VjCCzNwoWVlVUT5M8p5VnAmGDhBYD4/wpJvhffhUANc+HAsl2ozaH SkeRfCitbFLKWKtXQLwtb2rvONQMSAh9qLFv1q5FyVuRWqvHDJd7s7DoK998UgJg n2hck3UG4/kiDE76kgchi7YISioUgd081cGPmY4mtTJg8NEq5kVdASQxxTqtWpNM 9UdJ1fz8TpxB9X8D/szx330WunGoiFEz15Ia71k7tEaB1hqYvwrpfwvTCEqLFbRC 5gHq9yKlpD5T4gJLYiLsH+R2Ceh5YI1mlNttzn86Ukb2nqOh3r4KzEvXuW1ZGZnL bG4d1L0hEmJJkWdTz6XXnw6W0xZDzNr317lUfey35ASFgR6d4mRSdgN19FTTmkVg +6zxOsrZ0PS69vTaUHVjYAq3sbVGXrsyzNkBN9o5RU0O65SvimGujr0aBaIDmXkw 9O2TcnTEjP4j7NRT63tn =yj9f -----END PGP SIGNATURE----- --ZgN8q2zxDFUkdMnT3BGlRx1UpT5ovRvhq--
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