Date: Thu, 13 Jun 2013 07:05:26 +0800 From: Sergey Lobanov <wmn@siberianet.ru> To: freebsd-fs@freebsd.org Subject: Re: An order of magnitude higher IOPS needed with ZFS than UFS Message-ID: <201306130705.26895.wmn@siberianet.ru> In-Reply-To: <20130612114937.GA13688@icarus.home.lan> References: <51B79023.5020109@fsn.hu> <op.wykdduw834t2sn@markf.office.supranet.net> <20130612114937.GA13688@icarus.home.lan>
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On Wednesday 12 June 2013, Jeremy Chadwick wrote: > On Wed, Jun 12, 2013 at 06:40:32AM -0500, 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. > > Mark, do you have any references for this? I'd love to learn/read more > about this engineering/design aspect (I won't say flaw, I'll just say > aspect) to ZFS, as it's the first I've heard of it. > > The reason I ask: (respectfully, not judgementally) I'm worried you > might be referring to something that has to do with SSDs and not ZFS, > specifically SSD wear-levelling performing better with lots of free > space (i.e. a small FTL map; TRIM helps with this immensely) -- where > the performance hit tends to begin around the 70-80% mark. (I can talk > more about that if asked, but want to make sure the two things aren't > being mistaken for one another) http://lists.freebsd.org/pipermail/freebsd-fs/2013-March/016834.html CC'd mm@. -- ISP "SiberiaNet" System and Network Administrator
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