Date: Fri, 17 Sep 2010 11:45:59 -0500 From: Bryan Drewery <bryan@shatow.net> To: Jeremy Chadwick <freebsd@jdc.parodius.com> Cc: freebsd-fs@freebsd.org Subject: Re: what happens to pool if ZIL dies on ZFS v14 Message-ID: <4C939B47.6030701@shatow.net> In-Reply-To: <20100917163732.GA59537@icarus.home.lan> 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> <20100917163732.GA59537@icarus.home.lan>
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> I was under the impression ZFS still managed to utilise the ZIL when a > pool didn't have any "log" devices associated with it (possibly some > sort of statically-allocated amount of RAM?) > > You can search the FreeBSD lists for people continually advocating > vfs.zfs.zil_disable=1. There's even a couple blog posts from engineers > talking about how the only way to get their filers to behave decently > was to disable the ZIL[1][2][3]. In most (every?) cases I've seen where > someone advocates disabling the ZIL, pool details aren't provided, which > leads me to believe their pools have no "log" devices. > > Here's a better way to phrase my question: does vfs.zfs.zil_disable=1 do > anything if there aren't any "log" devices in use (in any pool)? > > > [1]: http://jmlittle.blogspot.com/2010/03/zfs-log-devices-review-of-ddrdrive-x1.html > [2]: http://blogs.sun.com/erickustarz/entry/zil_disable > [3]: http://weblog.etherized.com/posts/130 > > The ZIL is still used even without a dedicated log device. Disabling it is *stupid* in most cases. Same goes for disabling the ARC. There is a lot of FUD out there regarding ZFS tuning. The bottom line: don't tune; add more RAM. Bryan
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