Date: Fri, 27 Oct 2006 23:14:57 -0500 From: Eric Anderson <anderson@centtech.com> To: Steve Peterson <stevep-hv@zpfe.com> Cc: performance@freebsd.org Subject: Re: gvinum raid5 performance seems slow Message-ID: <4542D941.2070204@centtech.com> In-Reply-To: <6.2.3.4.0.20061027180329.020bed68@localhost> References: <6.2.3.4.0.20061027180329.020bed68@localhost>
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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. ------------------------------------------------------------------------
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