Date: Sun, 4 Aug 2013 14:09:37 -0400 From: Zaphod Beeblebrox <zbeeble@gmail.com> To: Kevin Day <toasty@dragondata.com> Cc: freebsd-fs <freebsd-fs@freebsd.org> Subject: Re: ZFS option vfs.zfs.cache_flush_disable=1 Message-ID: <CACpH0MfTtJcwVmK1k-=OM9%2Bkyv=p%2BGiiqNX1t5EmmmRfeDz2Ag@mail.gmail.com> In-Reply-To: <9F85D42E-D431-455E-8DFC-CEA7AC53F4BE@dragondata.com> References: <51FD867B.8070803@denninger.net> <9F85D42E-D431-455E-8DFC-CEA7AC53F4BE@dragondata.com>
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I think the gravamen of the original question is the effect of vfs.zfs.cache_flush_disable=1. You have roughly the following situation: user writes --->> zfs caches --->> controller cache --->> drive cache --->> disk The stated problem was that zfs flushes push not only the zfs caches to the controller, but also the controller caches to disk. If the zfs cache flush is disabled, does that mean, in a period of inactivity, that data written to zfs will possibly sit in the zfs cache and not make it to disk?
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