Date: Fri, 17 Sep 2010 19:01:34 +0200 From: Olivier Smedts <olivier@gid0.org> To: gil@vidals.net Cc: freebsd-fs@freebsd.org Subject: Re: what happens to pool if ZIL dies on ZFS v14 Message-ID: <AANLkTinpdzaVPhsKwBKsqzvNHthkpD3Mdq0LTbqZsUV=@mail.gmail.com> In-Reply-To: <AANLkTimd6ZKENg3-W-1DxOoR5mRcTb0mfRikznKWuBTD@mail.gmail.com> References: <AANLkTi=vYVG300nhMjkcLju=kQhBdPJDqyaXR0mG84%2Bp@mail.gmail.com> <4C9385B0.2080909@shatow.net> <AANLkTin0LwQz%2BWi5cBOcHuVqyOz3%2BfFR7YC_=f2L5CyX@mail.gmail.com> <AANLkTinbPK1rNK5hg=t7N=sqFLuh8sNrZT9DFC_ppXWF@mail.gmail.com> <20100917161847.GA58503@icarus.home.lan> <AANLkTi=NX6koyj_xmadrTw8OvgCATPA=EQnTPmAxNGpo@mail.gmail.com> <AANLkTimd6ZKENg3-W-1DxOoR5mRcTb0mfRikznKWuBTD@mail.gmail.com>
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2010/9/17 Gil Vidals <gvidals@gmail.com>: > First, let me say that I'm receiving excellent input from the FreeBSD > community. I'm new to FreeBSD and ZFS and this mailing list has been very > helpful. > > I'm running ZFSv14 on FreeBSD 8.1 AMD64 with 8GB of DDR3 RAM with two SSD= s - > one for the ZIL and the other for the L2ARC cache. > > zambia# zpool iostat -v 1 1 > =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 capacity =A0 =A0 operations =A0 = =A0bandwidth > pool =A0 =A0 =A0 =A0 =A0 =A0 =A0 used =A0avail =A0 read =A0write =A0 read= =A0write > ---------------- =A0----- =A0----- =A0----- =A0----- =A0----- =A0----- > tank =A0 =A0 =A0 =A0 =A0 =A0 =A06.57G =A0 921G =A0 =A0 =A00 =A0 =A0 11 = =A0 116K =A0 438K > =A0mirror =A0 =A0 =A0 =A0 =A06.57G =A0 921G =A0 =A0 =A00 =A0 =A0 =A05 =A0= 116K =A0 229K > =A0 =A0label/disk1 =A0 =A0 =A0 - =A0 =A0 =A0- =A0 =A0 =A00 =A0 =A0 =A03 = =A057.9K =A0 229K > =A0 =A0label/disk2 =A0 =A0 =A0 - =A0 =A0 =A0- =A0 =A0 =A00 =A0 =A0 =A03 = =A057.8K =A0 229K > =A0label/zilcache =A0 136K =A059.5G =A0 =A0 =A00 =A0 =A0 =A06 =A0 =A0 17 = =A0 209K > cache =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 - =A0 =A0 =A0- =A0 =A0 =A0- =A0 =A0= =A0- =A0 =A0 =A0- =A0 =A0 =A0- > =A0label/l2cache =A0 59.6G =A08.50K =A0 =A0 =A00 =A0 =A0 =A00 =A031.5K = =A048.9K > ---------------- =A0----- =A0----- =A0----- =A0----- =A0----- =A0----- > > Observing the ZIL Cache, I see it being used very sparingly. And now that= I > know the SSD slog must be mirrored in ZFS < v19, I think the best course = of > action (assuming I'm not buying more equipment) is to mirror the ZIL SSD = and > abandon the L2ARC altogether. Won't RAM be used for L2ARC instead? Maybe 64G of ZIL is a bit much for your workload, too (I saw somewhere it must be the size of 30s of sustained write to your pool). You could also make two partitions on your SSDs, mirror the ZIL on one partition of each SSD, and add the remaining partitions (not mirrored - useless) for the L2ARC. I'm assuming you have identical SSDs. If you have for example en MLC and an SLC, prefer the SLC for ZIL. Cheers > > --Gil Vidals / VMRacks.com > > On Fri, Sep 17, 2010 at 9:21 AM, Freddie Cash <fjwcash@gmail.com> wrote: > >> On Fri, Sep 17, 2010 at 9:18 AM, Jeremy Chadwick >> <freebsd@jdc.parodius.com> wrote: >> > On Fri, Sep 17, 2010 at 09:17:11AM -0700, Freddie Cash wrote: >> >> On Fri, Sep 17, 2010 at 8:35 AM, Gil Vidals <gvidals@gmail.com> wrote= : >> >> > Bryan thank you for the detailed answer. >> >> > >> >> > Assuming the ZIL SSD died, what steps would I follow to recover the >> pool? (i >> >> > hope it is recoverable). >> >> >> >> If you are running ZFSv1 through ZFSv18 and your log device dies, you= r >> >> pool is dead, gone, unrecoverable, no secret prize, no continues, do >> >> not pass go, etc, etc, etc. >> >> >> >> If you are running ZFSv19 or newer and your log device dies, you can >> >> remove the dead device and carry on. =A0You will lose any data that w= as >> >> in the ZIL, but the pool will be intact. >> > >> > Given the severity of this predicament, then why is it people are >> > disabling the ZIL (via vfs.zfs.zil_disable=3D1) ? >> >> I'm not sure what you mean by that. >> >> This (dead ZIL =3D=3D dead pool) only applies to separate log (slog) dev= ices. >> >> -- >> Freddie Cash >> fjwcash@gmail.com >> _______________________________________________ >> freebsd-fs@freebsd.org mailing list >> http://lists.freebsd.org/mailman/listinfo/freebsd-fs >> To unsubscribe, send any mail to "freebsd-fs-unsubscribe@freebsd.org" >> > _______________________________________________ > freebsd-fs@freebsd.org mailing list > http://lists.freebsd.org/mailman/listinfo/freebsd-fs > To unsubscribe, send any mail to "freebsd-fs-unsubscribe@freebsd.org" > --=20 Olivier Smedts=A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 = =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0=A0 _ =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0= =A0 ASCII ribbon campaign ( ) e-mail: olivier@gid0.org=A0 =A0 =A0 =A0 - against HTML email & vCards=A0 X www: http://www.gid0.org=A0 =A0 - against proprietary attachments / \ =A0 "Il y a seulement 10 sortes de gens dans le monde : =A0 ceux qui comprennent le binaire, =A0 et ceux qui ne le comprennent pas."
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