Date: Sun, 16 Jun 2013 10:20:00 +0200 From: Attila Nagy <bra@fsn.hu> To: Mark Felder <feld@feld.me> Cc: freebsd-fs@freebsd.org Subject: Re: An order of magnitude higher IOPS needed with ZFS than UFS Message-ID: <51BD7530.9060000@fsn.hu> In-Reply-To: <op.wykdduw834t2sn@markf.office.supranet.net> References: <51B79023.5020109@fsn.hu> <op.wykdduw834t2sn@markf.office.supranet.net>
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On 06/12/13 13:40, Mark Felder wrote: > On Tue, 11 Jun 2013 16:01:23 -0500, Attila Nagy <bra@fsn.hu> wrote: > >> BTW, the file systems are 77-78% full according to df (so ZFS holds >> more, because UFS is -m 8). > > ZFS write performance can begin to drop pretty badly when you get > around 80% full. I've not seen any benchmarks showing an improvement > with a very fast and large ZIL or tons of memory, but I'd expect that > would help significantly. Just note that you're right at the edge > where performance gets impacted. I'm aware of that, even thought about it, that's why I wrote the disk free percents into my mail. I see a completely normal write pattern, but a lot of reads, so I guess ZIL wouldn't help here (maybe L2ARC or more memory, if something doesn't fit into it). BTW, I think having the allowed fill value this low (UFS has the breakdown point much higher) is of a really bad design...
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