Date: Tue, 22 Jan 2019 12:52:59 +0100 From: Borja Marcos <borjam@sarenet.es> To: Steven Hartland <killing@multiplay.co.uk> Cc: jdelisle <jdelisle@gmail.com>, freebsd-fs <freebsd-fs@freebsd.org> Subject: Re: ZFS on Hardware RAID Message-ID: <A593D329-3526-4B5A-BCEF-7C17FA5FFA49@sarenet.es> In-Reply-To: <335e44ec-7c76-8dbd-f587-46e6a9266efc@multiplay.co.uk> 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> <alpine.BSF.2.21.1901200930550.12592@mail0.time-domain.co.uk> <CAMdBLfQvF7mXriwAvu-h5BaXBNhb_8VPRRfDmeM0u1NGoyWY_g@mail.gmail.com> <92746659-4B3F-415C-BB6A-6C99837AFAF2@sarenet.es> <335e44ec-7c76-8dbd-f587-46e6a9266efc@multiplay.co.uk>
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> On 21 Jan 2019, at 16:40, Steven Hartland <killing@multiplay.co.uk> = wrote: >=20 >>=20 > Typically yes it does. >> The same could be said of other functionalities available when you = talk directly >> to the disks. >>=20 >>=20 >>=20 >>> That's why I did as I describe above. I didn't have the money to = buy an >>> HBA until a year or two later, and I had good backups, so I used the = PERC >>> 6/e. >>>=20 >> Depending on the LSI model used in that card you can make it behave = like an HBA.=20 >>=20 >>=20 > Indeed you can for most, but its not an easy or error free option, = requires force flashing from IR to IT firmware, and if it goes wrong you = can end up with a bricked controller. >=20 > We've used LSI's in IR mode (RAID) but as individual disks JBOD with = ZFS raid2z or mirroring on top for a long time and on lots of machines, = not had any issues to report. So while I would never use hardware RAID = from those controllers with ZFS, JBOD on them is an easy and reliable = option in our experience. Sorry to insist, but maybe we are talking of different stuff? My = apologies in advance if I am confused and/or my information is outdated.=20 JBOD mode: a mode offered by some LSI Logic IR controllers to create = virtual devices mapped so that each one is effectively. For example, with the mfi driver the =E2=80=9Cdisks=E2=80=9D appear as = =E2=80=9Cmfisyspd=E2=80=9D devices while the =E2=80=9Cconventional=E2=80=9D= logical volumes appear as=20 =E2=80=9Cmfid=E2=80=9D. My information could be outdated though?=20 HBA mode: when the card is in IT mode *or* it does expose the actual = targets to the CAM layer. In the past I did it by manually patching the drivers and I=E2=80=99ve kept systems running = smoothly for many years despite using IR cards.=20 Currently you can use hw.mfi.allow_cam_disk_passthrough tunable to = achieve the same effect without ugly tinkering.=20 Unless I am terribly wrong, when I tried the JBOD mode as defined above = (with LSI SAS3 cards and IR firmware) the mfisyspd devices were not actual CAM devices.=20 Actually I find =E2=80=9CJBOD=E2=80=9D an artificial and confusing term = because it can mean so many things. I would have rather preferred LSI to avoid it and provide either real, transparent access to the = actual targets insteaf of somewhat =E2=80=9Cvirtualizing=E2=80=9D them. Again, I may be confused? I haven=E2=80=99t tried to configure a LSI IR = card as =E2=80=9CJBOD=E2=80=9D for a long time. Maybe now they do expose the targets instead of defining logical volumes? Thanks! Borja.
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