Date: Tue, 29 Sep 2009 12:45:20 +0200 From: Attila Nagy <bra@fsn.hu> To: freebsd-fs@FreeBSD.org Subject: ARC size constantly shrinks, then ZFS slows down extremely Message-ID: <4AC1E540.9070001@fsn.hu>
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Hello, I'm using FreeBSD 8 (previously 7) on a machine with a lot of disks and 32 GB RAM. With 7.x it ran very well for about 50 days, but suddenly every operation have slowed down. gstat showed that the disks are working a lot more than usual the zpool/zfs was pretty unusable. I've rebooted the machine then with FreeBSD 8 in the hope the new ZFS fixes will correct this issue (no 50 days have passed since then, so I don't know yet) and started to monitor ZFS's statistics. It seems that after a reboot, the ARC size starts to grow, then something flips the switch and it changes to shrinking, instead of maintaining the size. Please see the pictures here: http://people.fsn.hu/~bra/freebsd/20090929-zfs-arcsize/ Before the 27th, the machine ran FreeBSD 7, after that date it runs 8. As you can see, no user process tooks the memory, so I don't know why the ARC size grows first and then start to decrease. Could it be that the ARC size decreases such a big amount that it effectively disappears and this causes the IO activity go up and kill the machine? Thanks,
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