Date: Fri, 23 Jul 2010 15:29:51 +0200 From: Ivan Voras <ivoras@freebsd.org> To: freebsd-fs@freebsd.org Subject: Re: ZFS makes SSDs faster than memory! Message-ID: <i2c5fn$uhh$1@dough.gmane.org> In-Reply-To: <4C499733.5000104@fsn.hu> References: <4C496EB0.7050004@fsn.hu> <i2c14p$g4f$1@dough.gmane.org> <20100723125051.GM53114@cicely7.cicely.de> <4C499733.5000104@fsn.hu>
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On 07/23/10 15:20, Attila Nagy wrote: > Maybe I should have written this first, but I'm not the only one reading > from the machine. You probably realize this makes all your performance data of suspicious validity :) > For random reads even the cheapest MLC outperforms a 7k2 SATA disk (only > reads), and this is an Intel stuff, which can do 3000 RIOPS easily. >> Are there any facts backup your assumption that data is really >> read from memory, SSD, disk in the named cases? >> E.g. by ARC/L2ARC and IO statistics. >> > Yes. When downloading from L2ARC: > L(q) ops/s r/s kBps ms/r w/s kBps ms/w %busy Name > 0 174 174 21505 0.8 0 0 0.0 13.3| ad4 > 0 169 169 21479 0.9 0 0 0.0 15.0| ad6 > when downloading from ARC: > L(q) ops/s r/s kBps ms/r w/s kBps ms/w %busy Name > 0 26 19 1129 0.6 7 78 0.4 1.3| ad4 > 0 19 12 1436 1.1 7 78 0.3 1.4| ad6 So it looks like you encountered a problem where the memory-based ARC cache read performance is incredibly bad?
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