Michelle Sullivan http://www.mhix.org/ Sent from my iPad
> On 03 May 2019, at 22:51, Kevin P. Neal <k...@neutralgood.org> wrote: > > On Fri, May 03, 2019 at 08:25:08PM +1000, Michelle Sullivan wrote: >>> 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. > > I have an old Dell R610 with a PERC 6/i and Megaraid SAS driver Ver 4.23. > When I use mfiutil to set caching to write through it still goes through > the cache. Which means that if a drive fails and the machine reboots the > firmware stops the boot because it has data in the cache that it wants > to store on the failed drive. So a normal failure of a drive in a three > way ZFS mirror that shouldn't cause a loss of service actually does. > I don’t think it will do that in write through.. it will everytime in write back. > Thumbs down to RAID cards. > -- > Kevin P. Neal http://www.pobox.com/~kpn/ > > "Good grief, I've just noticed I've typed in a rant. Sorry chaps!" > Keir Finlow Bates, circa 1998 > _______________________________________________ > 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"