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: > > > >> On 3 May 2019, at 11:55, Pete French <petefre...@ingresso.co.uk> wrote: >> >> >> >>> On 03/05/2019 08:09, Borja Marcos via freebsd-stable wrote: >>> >>> The right way to use disks is to give ZFS access to the plain CAM devices, >>> not thorugh some so-called JBOD on a RAID >>> controller which, at least for a long time, has been a *logical* “RAID0” >>> 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 >>> drivers to enabling a sysctl tunable or even >>> flashing the card to turn it into a plain HBA with no RAID features (or >>> minimal ones). >> >> Oddly enough I got bitten by something like this yesteray. I have a machine >> 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 definitely not write back with bad bbu) seemed to solve it. Michelle >> >> BSD seems them as da0, da1, da2, da3 - but the RAID controller oly presents >> one of them to the BIOS, so my booting has to be all from that drive. This >> has been da0 for as long as I can remember, but yesteday it decided to start >> using what BSD sees as da1. Of course this is very hard to recognise as da0 >> and da1 are pretty much mirrors of each other. Spent a long time trying to >> work out why the fixes I was applying to da0 were not being used at boot >> time. > > Hmm What happens when you do a “camcontrol devlist”? > > Camcontrol tags da0 -v? > > How is the controller recognized by FreeBSD? For some of them it’s 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 > case. > > 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. > > For mfi recognized cards there is a tunable: hw.mfi.allow_cam_disk_passthrough > > For aac cards it was a matter of commenting a couple of source code lines in > the driver (at your own risk of course). I’ve been running a > server for years doing that. > > > > > > > Borja. > > > _______________________________________________ > freebsd-stable@freebsd.org mailing list > https://lists.freebsd.org/mailman/listinfo/freebsd-stable > To unsubscribe, send any mail to "freebsd-stable-unsubscr...@freebsd.org" _______________________________________________ freebsd-stable@freebsd.org mailing list https://lists.freebsd.org/mailman/listinfo/freebsd-stable To unsubscribe, send any mail to "freebsd-stable-unsubscr...@freebsd.org"
