Date: Tue, 23 Feb 2010 22:21:41 +0100 From: Ivan Voras <ivoras@freebsd.org> To: ticso@cicely.de Cc: freebsd-fs@freebsd.org Subject: Re: Some ZFS+NFS benchmarks (OpenSolaris) Message-ID: <9bbcef731002231321t352ce3e6y5fdafbf75b7fac54@mail.gmail.com> In-Reply-To: <20100223193458.GO13767@cicely7.cicely.de> References: <hm19h4$8ah$1@dough.gmane.org> <20100223193458.GO13767@cicely7.cicely.de>
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On 23 February 2010 20:34, Bernd Walter <ticso@cicely7.cicely.de> wrote: > On Tue, Feb 23, 2010 at 08:15:48PM +0100, Ivan Voras wrote: >> http://staff.science.uva.nl/~delaat/sne-2009-2010/p02/report.pdf >> >> It's curious how ZIL on SSD doesn't help them with NFS when they >> increase the load. > > My assumption is because they already write linear on SSD and get a more > or less fixed write rate, while parallel write rate with disks can > increase because of reordering. > > I'm personally impressed by my own tests on how much our current > USB stack can speed up random reads even with cheap USB flash sticks > used as cache devices. This is surprising to hear - I've just run some randomio (http://www.arctic.org/~dean/randomio/) tests on two little used USB flash sticks and got around 110 IOPS sequential writing (~~ 7 MB/s) and a bit less than 30 IOPS random writes of 4 KB buffers (amounting to ~~ 1 MB/s). (the test command was "randomio file 16 1 1 4096 10"). The ZIL should be written practically linearly - the sequential write rate is relevant here - and it is actually significantly slower than what mechanical HDDs can achieve. Is your result with ZIL perhaps simply because you moved it to another device and so freed the main device?
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