Date: Fri, 03 May 2019 23:07:51 +1000 From: Michelle Sullivan <michelle@sorbs.net> To: "Kevin P. Neal" <kpn@neutralgood.org> Cc: freebsd-stable@freebsd.org, Borja Marcos <borjam@sarenet.es>, Pete French <petefrench@ingresso.co.uk> Subject: Re: ZFS... Message-ID: <2A7B5457-371A-4014-8C1E-972BA2FD10DF@sorbs.net> In-Reply-To: <20190503125118.GA11226@neutralgood.org> References: <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> <62803130-9C40-4A98-B5A4-A2DFAC0FAD65@sorbs.net> <20190503125118.GA11226@neutralgood.org>
next in thread | previous in thread | raw e-mail | index | archive | help
Michelle Sullivan http://www.mhix.org/ Sent from my iPad > On 03 May 2019, at 22:51, Kevin P. Neal <kpn@neutralgood.org> wrote: >=20 > 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-stabl= e@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 devi= ces, not thorugh some so-called JBOD on a RAID >>>>> controller which, at least for a long time, has been a *logical* =E2=80= =9CRAID0=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 sourc= e drivers to enabling a sysctl tunable or even >>>>> flashing the card to turn it into a plain HBA with no RAID features (o= r minimal ones). >>>>=20 >>>> Oddly enough I got bitten by something like this yesteray. I have a mac= hine containing an HP P400 RAID controller, which is nice enough, but I run Z= FS so I have made the drives all into RAID-0 as being as close as I can get t= o accessing the raw SAS drives. >>=20 >> I got bitten by that on this hardware originally... switching to raid-0 a= nd separate drives then switching to write-through (not write back and defin= itely not write back with bad bbu) seemed to solve it. >=20 > 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. >=20 I don=E2=80=99t think it will do that in write through.. it will everytime i= n write back. > Thumbs down to RAID cards. > --=20 > Kevin P. Neal http://www.pobox.com/~kpn/ >=20 > "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-unsubscribe@freebsd.org"
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?2A7B5457-371A-4014-8C1E-972BA2FD10DF>