Date: Fri, 03 May 2019 20:25:08 +1000 From: Michelle Sullivan <michelle@sorbs.net> To: Borja Marcos <borjam@sarenet.es> Cc: Pete French <petefrench@ingresso.co.uk>, freebsd-stable@freebsd.org Subject: Re: ZFS... Message-ID: <62803130-9C40-4A98-B5A4-A2DFAC0FAD65@sorbs.net> In-Reply-To: <C5403ADD-86C1-4184-BDA6-DA8C7426458E@sarenet.es> References: <30506b3d-64fb-b327-94ae-d9da522f3a48@sorbs.net> <CAOtMX2gf3AZr1-QOX_6yYQoqE-H%2B8MjOWc=eK1tcwt5M3dCzdw@mail.gmail.com> <56833732-2945-4BD3-95A6-7AF55AB87674@sorbs.net> <3d0f6436-f3d7-6fee-ed81-a24d44223f2f@netfence.it> <17B373DA-4AFC-4D25-B776-0D0DED98B320@sorbs.net> <70fac2fe3f23f85dd442d93ffea368e1@ultra-secure.de> <70C87D93-D1F9-458E-9723-19F9777E6F12@sorbs.net> <CAGMYy3tYqvrKgk2c==WTwrH03uTN1xQifPRNxXccMsRE1spaRA@mail.gmail.com> <fe6880bc-d40a-2377-6bea-28bfd8229e9f@sorbs.net> <58DA896C-5312-47BC-8887-7680941A9AF2@sarenet.es> <cde21bb4-d741-3300-077f-745cfc343aa9@ingresso.co.uk> <C5403ADD-86C1-4184-BDA6-DA8C7426458E@sarenet.es>
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Michelle Sullivan http://www.mhix.org/ Sent from my iPad > On 03 May 2019, at 20:09, Borja Marcos via freebsd-stable <freebsd-stable@= freebsd.org> wrote: >=20 >=20 >=20 >> On 3 May 2019, at 11:55, Pete French <petefrench@ingresso.co.uk> wrote: >>=20 >>=20 >>=20 >>> On 03/05/2019 08:09, Borja Marcos via freebsd-stable wrote: >>>=20 >>> The right way to use disks is to give ZFS access to the plain CAM device= s, not thorugh some so-called JBOD on a RAID >>> controller which, at least for a long time, has been a *logical* =E2=80=9C= RAID0=E2=80=9D volume on a single disk. That additional layer can >>> completely break the semantics of transaction writes and cache flushes. >>> With some older cards it can be tricky to achieve, from patching source d= rivers to enabling a sysctl tunable or even >>> flashing the card to turn it into a plain HBA with no RAID features (or m= inimal ones). >>=20 >> Oddly enough I got bitten by something like this yesteray. I have a machi= ne containing an HP P400 RAID controller, which is nice enough, but I run ZFS= so I have made the drives all into RAID-0 as being as close as I can get to= accessing the raw SAS drives. I got bitten by that on this hardware originally... switching to raid-0 and= separate drives then switching to write-through (not write back and definit= ely not write back with bad bbu) seemed to solve it. Michelle >>=20 >> BSD seems them as da0, da1, da2, da3 - but the RAID controller oly presen= ts one of them to the BIOS, so my booting has to be all from that drive. Thi= s has been da0 for as long as I can remember, but yesteday it decided to sta= rt using what BSD sees as da1. Of course this is very hard to recognise as d= a0 and da1 are pretty much mirrors of each other. Spent a long time trying t= o work out why the fixes I was applying to da0 were not being used at boot t= ime. >=20 > Hmm What happens when you do a =E2=80=9Ccamcontrol devlist=E2=80=9D? >=20 > Camcontrol tags da0 -v? >=20 > How is the controller recognized by FreeBSD? For some of them it=E2=80=99s= possible to instruct the controller to present the physical devices to CAM.= Of course > you need to be careful to avoid any logical volume configuration in that c= ase.=20 >=20 > But I would only tinker with this at system installation time, making such= a change on a running system with valid data can be disastrous. >=20 > For mfi recognized cards there is a tunable: hw.mfi.allow_cam_disk_passthr= ough >=20 > For aac cards it was a matter of commenting a couple of source code lines i= n the driver (at your own risk of course). I=E2=80=99ve been running a=20 > server for years doing that. >=20 >=20 >=20 >=20 >=20 >=20 > Borja. >=20 >=20 > _______________________________________________ > freebsd-stable@freebsd.org mailing list > https://lists.freebsd.org/mailman/listinfo/freebsd-stable > To unsubscribe, send any mail to "freebsd-stable-unsubscribe@freebsd.org"
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