Date: Sun, 8 Aug 1999 16:40:24 +0930 From: Greg Lehey <grog@lemis.com> To: Andreas Klemm <andreas@klemm.gtn.com> Cc: John-Mark Gurney <gurney_j@resnet.uoregon.edu>, cvs-committers@FreeBSD.org, cvs-all@FreeBSD.org Subject: Re: cvs commit: src/sys/dev/vinum vinuminterrupt.c Message-ID: <19990808164024.E10056@freebie.lemis.com> In-Reply-To: <19990808085758.A2467@titan.klemm.gtn.com>; from Andreas Klemm on Sun, Aug 08, 1999 at 08:57:59AM %2B0200 References: <199908070806.BAA66984@freefall.freebsd.org> <19990807181938.49481@hydrogen.fircrest.net> <19990808105939.A10056@freebie.lemis.com> <19990808085758.A2467@titan.klemm.gtn.com>
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On Sunday, 8 August 1999 at 8:57:59 +0200, Andreas Klemm wrote: > On Sun, Aug 08, 1999 at 10:59:39AM +0930, Greg Lehey wrote: >> On Saturday, 7 August 1999 at 18:19:38 -0700, John-Mark Gurney wrote: >>> Greg Lehey scribbled this message on Aug 7: >>>> Import RAID-5 code. >>>> 1.12 +224 -3 src/sys/dev/vinum/vinuminterrupt.c >>> >>> so, does this mean that you can use RAID-5 w/o having to buy anything? >> >> Yes. > > How fast would RAID5 be with a AHA2940 and 3 IBM DORS disks connected to > it (5400U/Min, 5.4 MB/sec using bonnie). Is it still fast, 50% of speed ... That depends on what you're doing. bonnie doesn't really tell you very much; you need to measure the raw throughput. Also, it depends on what kind of load you're putting on it. Do you intend to have multiple processes accessing the volume at the same time? What's your read/write ratio? RAID-5 is slow on writes, but fast enough on reads. Having said that, 3 drives isn't very much for RAID-5. You use a third of the space for parity, and you don't get the read performance benefits that you'd get with more drives. To measure both conventional drives and Vinum volumes, use rawio (ftp://ftp.lemis.com/pub/rawio.tar.gz). > I know difficult to say ... but only want to know, if it's a doable > compromise instead of doing hardware RAID... There's currently no reason to believe that hardware RAID will give you better performance until you start to max out the CPU, which appears unlikely. Greg -- See complete headers for address, home page and phone numbers finger grog@lemis.com for PGP public key To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe cvs-all" in the body of the message
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