Date: Sat, 28 Oct 2006 22:19:17 +0300 From: Petri Helenius <pete@he.iki.fi> To: Steve Peterson <stevep-hv@zpfe.com> Cc: performance@freebsd.org Subject: Re: gvinum raid5 performance seems slow Message-ID: <4543AD35.30205@he.iki.fi> In-Reply-To: <6.2.3.4.0.20061028124559.02105930@localhost> References: <6.2.3.4.0.20061027180329.020bed68@localhost> <4542D941.2070204@centtech.com> <6.2.3.4.0.20061028124559.02105930@localhost>
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According to my understanding vinum does not overlap requests to multiple disks when running in raid5 configuration so you're not going to achieve good numbers with just "single stream" tests. Pete Steve Peterson wrote: > 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" > > > _______________________________________________ > 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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