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Message-ID: <alpine.DEB.2.00.0910091814470.14413@sebohet.brgvxre.pu> Date: Fri, 9 Oct 2009 18:44:12 +0200 (CEST) From: Tobias Oetiker <tobi@...iker.ch> To: linux-kernel@...r.kernel.org Subject: Linux IO service time - a perfect source of randomness ? I have just completed extensive benchmarking of ext3 on 2.6.31.2 both on HW RAID6 as well as single Hard Drive. I have written a new file system benchmark that creates load by reading and writing large file trees in paralle to simulate a busy fileserver. The results are as follows: * as soon as the system comes under strain the service time for single io operations becomes almost random with huge outliers of several seconds. * on HW RAID the best performance is to be gained with data=ordered and cfq scheduler * on single HDD setups, only (!) data=writeback with cfq provides good performance. * the deadline scheduler did not perform well in any of the read/write scenarios. * btrfs has fantastic read performance but does not (yet?) do well when readers and writers are competing. my report is on http://insights.oetiker.ch/linux/fsopbench/ cheers tobi -- Tobi Oetiker, OETIKER+PARTNER AG, Aarweg 15 CH-4600 Olten, Switzerland http://it.oetiker.ch tobi@...iker.ch ++41 62 775 9902 / sb: -9900 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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