Date: Sun, 20 Jan 2019 09:33:46 -0600 From: jdelisle <jdelisle@gmail.com> To: andy thomas <andy@time-domain.co.uk> Cc: Maciej Jan Broniarz <gausus@gausus.net>, freebsd-fs <freebsd-fs@freebsd.org> Subject: Re: ZFS on Hardware RAID Message-ID: <CAMdBLfQvF7mXriwAvu-h5BaXBNhb_8VPRRfDmeM0u1NGoyWY_g@mail.gmail.com> In-Reply-To: <alpine.BSF.2.21.1901200930550.12592@mail0.time-domain.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>
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On Sun, Jan 20, 2019 at 9:04 AM andy thomas <andy@time-domain.co.uk> wrote: > I don't h/w RAID controllers do any parity checking, etc for RAID 0 > virtual disks containing only one disk? > I can say for certain that with Dell PERC 6/e RAID (SAS 8087ELP based) cards, when the virtual devices are entire disks each in a RAID0 configuration, the way the adapter writes data to them is effectively the same as JBOD. You can take a RAID0 drive from a PERC 6/e controller and use in with an HBA/ "IT Mode" JBOD controller without issue. I personally migrated 14x 1TB drives off PERC 6/e (all RAID0's) to a SAS 6gbps HBA, and my ZFS VDEV's and pools were totally fine. You can move back and forth no problem. I can't say this is the case for ALL RAID controllers, I've only done this with an old PERC 6/e. > I know ZFS on h/w raid can't possibly be optimal and use of JBOD, > pass-thru or plain HBA is to be preferred at all times but older RAID > controllers don't support non-RAID operation - after all, h/w RAID > controller design is primarily intended for the Windows Server market > where Windows didn't support any kind of software RAID scheme at that time > (it might do know, I don't know). > 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.
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