Date: Fri, 26 Aug 2011 15:18:51 +0100 From: Johannes Totz <jtotz@imperial.ac.uk> To: freebsd-fs@freebsd.org Subject: Monitoring zfs arc size (for tuning) Message-ID: <j38a0b$cu6$1@dough.gmane.org>
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Heya, I've been monitoring my arc size, hit and miss rates etc to determine what a minimum arc size would be without performance going down the drain, for my workload. The only interesting point so far is that arc size still exceeds its limit occasionally! That is, kstat.zfs.misc.arcstats.size is larger than kstat.zfs.misc.arcstats.c_max (which is the same as vfs.zfs.arc_max) by a few hundred megabytes. Also, some of the periodic tasks that this machine does makes kstat.zfs.misc.arcstats.size go down to almost zero, and then shoot up to the max again in a short period of time. This is on: FreeBSD XXX 8.2-STABLE FreeBSD 8.2-STABLE #0 r224227: Wed Jul 20 16:55:23 BST 2011 root@XXX:/usr/obj/usr/src/sys/GENERIC amd64 Johannes
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