Date: Sat, 28 Oct 2006 12:52:14 -0500 From: Steve Peterson <stevep-hv@zpfe.com> To: Eric Anderson <anderson@centtech.com>,performance@freebsd.org Subject: Re: gvinum raid5 performance seems slow Message-ID: <6.2.3.4.0.20061028124559.02105930@localhost> In-Reply-To: <4542D941.2070204@centtech.com> References: <6.2.3.4.0.20061027180329.020bed68@localhost> <4542D941.2070204@centtech.com>
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Eric -- thanks for looking at my issue. Here's a dd reading from one of the disks underlying the array (the others have basically the same performance): $ time dd if=/dev/ad10 of=/dev/null bs=1m count=1000 1000+0 records in 1000+0 records out 1048576000 bytes transferred in 15.322421 secs (68434095 bytes/sec) 0.008u 0.506s 0:15.33 3.2% 20+2715k 0+0io 0pf+0w and here's a dd reading from the raw gvinum device /dev/gvinum/vol1: $ time dd if=/dev/gvinum/vol1 of=/dev/null bs=1m count=1000 1000+0 records in 1000+0 records out 1048576000 bytes transferred in 25.870684 secs (40531437 bytes/sec) 0.006u 0.552s 0:25.88 2.1% 23+3145k 0+0io 0pf+0w Is there a way to nondestructively write to the raw disk or gvinum device? For comparison, here's a read against the raw PATA device on the machine: $ time dd if=/dev/ad0 of=/dev/null bs=1m count=1000 1000+0 records in 1000+0 records out 1048576000 bytes transferred in 26.096070 secs (40181376 bytes/sec) 0.013u 0.538s 0:26.10 2.0% 24+3322k 0+0io 0pf+0w Steve At 11:14 PM 10/27/2006, Eric Anderson wrote: >On 10/27/06 18:03, Steve Peterson wrote: >>I recently set up a media server for home use and decided to try >>the gvinum raid5 support to learn about it and see how it >>performs. It seems slower than I'd expect -- a little under >>6MB/second, with about 50 IOs/drive/second -- and I'm trying to >>understand why. Any assistance/pointers would be appreciated. >>The disk system consists of 4 Seagate NL35 SATA ST3250623NS drives >>connected to a Promise TX4300 (PDC40719) controller, organized as a >>RAID5 volume via gvinum using this configuration: >>drive drive01 device /dev/ad10 >>drive drive02 device /dev/ad6 >>drive drive03 device /dev/ad4 >>drive drive04 device /dev/ad8 >>volume vol1 >> plex org raid5 256k >> sd length 200001m drive drive01 >> sd length 200001m drive drive02 >> sd length 200001m drive drive03 >> sd length 200001m drive drive04 >>dd reports the following performance on a 1G file write to the >>RAID5 hosted volume: >>$ time dd if=/dev/zero of=big.file bs=1m count=1000 >>1000+0 records in >>1000+0 records out >>1048576000 bytes transferred in 179.717742 secs (5834571 bytes/sec) >> 179.76 real 0.02 user 16.60 sys >>By comparison, creating the same file on the system disk (an old >>ATA ST380021A connected via a SIS 730 on the motherboard): >>time dd if=/dev/zero of=big.file bs=1m count=1000 >>1000+0 records in >>1000+0 records out >>1048576000 bytes transferred in 28.264056 secs (37099275 bytes/sec) >> 28.32 real 0.01 user 19.13 sys >>and vmstat reports about 280-300 IOs/second to that drive. >>The CPU is pretty weak -- an Athlon 750. Is that the source of my >>problem? If you look at the vmstat output below the machine is >>busy but not pegged. > > >Try the dd to the raw gvinum device instead of through a filesystem, >and also to the individual disks. That will at least tell us where to look. > > >Eric > > > >-- >------------------------------------------------------------------------ >Eric Anderson Sr. Systems Administrator Centaur Technology >Anything that works is better than anything that doesn't. >------------------------------------------------------------------------ >_______________________________________________ >freebsd-performance@freebsd.org mailing list >http://lists.freebsd.org/mailman/listinfo/freebsd-performance >To unsubscribe, send any mail to "freebsd-performance-unsubscribe@freebsd.org"
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