Date: Tue, 05 Jul 2016 21:07:24 +0200 From: Michelle Sullivan <michelle@sorbs.net> To: "freebsd-fs@freebsd.org" <freebsd-fs@freebsd.org> Subject: Re: resilver slowdown.... Message-ID: <577C056C.7070108@sorbs.net> In-Reply-To: <577BA643.6040206@sorbs.net> References: <577BA643.6040206@sorbs.net>
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Michelle Sullivan wrote: > After retuning for priority to the resilver, I see massive (very good) > performance.... then at some random time later (or so it seemed) the > performance would drop off very quickly always at least to half the > performance, sometimes as much as a quarter of the speed... > > > At first I though it was memory based, then observing system with 19G > (of 32G) free figured it must be based on the stuff on the disk got > some 16T of very small files, and another 16T of video files so > figured it was probably going from large files to small files etc... > Nope, after a reboot and resetting the tuning params to the same each > time after the reboot I'd be seeing an immediate and sustained > performance... Watching it more it seems this is directly related: > > [root@colossus ~]# sysctl -a | grep \\.arc_ > vfs.zfs.arc_meta_limit: 4294967296 > vfs.zfs.arc_meta_used: 5529107352 > vfs.zfs.arc_min: 8589934592 > vfs.zfs.arc_max: 17179869184 Yup think it is related to the meta_limit and meta_used... Resilvering at 203M/s (according to zpool status) [root@colossus ~]# sysctl -a | grep \\.arc_ vfs.zfs.arc_meta_limit: 4294967296 vfs.zfs.arc_meta_used: 2187549528 vfs.zfs.arc_min: 8589934592 vfs.zfs.arc_max: 17179869184 Noticed it had slowed again.. around 64M/s ... [root@colossus ~]# sysctl -a | grep \\.arc_ vfs.zfs.arc_meta_limit: 4294967296 vfs.zfs.arc_meta_used: 4295111952 vfs.zfs.arc_min: 8589934592 vfs.zfs.arc_max: 17179869184 Rebooted and back to >120M/s (can't get a reading atm - too soon after the reboot) -- Michelle Sullivan http://www.mhix.org/
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