Date: Sat, 23 Nov 2002 22:21:52 -0500 From: "Charles Swiger" <cswiger@mac.com> To: <stable@FreeBSD.ORG> Subject: Re: RAID performance problems Message-ID: <01de01c29368$a2893ca0$0301a8c0@prime> References: <E18FfTI-0004KM-00@mailhost.firstcallgroup.co.uk>
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Pete French wrote: [ ... ] > 1) a 15k RPM drive attached directly to an Adaptec SCSI controller > 2) a RAID-1 mirrored pair of 10k RPS drives > 3) a RAID-5 set of 5 7200 RPM drives > > All SCSI buses are 40MB/sec. Both the RAID drives are being run from > the same Compaq 4200 RAID controller. Both the RAID controller and > the Adaptec SCSI card are on the same PCI bus. > > So, what I expected was that the driect drive would be fastest, > followed by the RAID-1, then the RAID-5 (at least as far as write > performance goes) You're not going to be able to derive firm conclusions from changing two variables at a time, unless you fill in the other missing pieces. Try comparing one of the five 7200 RPM drives via direct I/O versus two 7200 RPM drives in a RAID-1 mirror, versus the RAID-5 case. If you're using hardware RAID, then FreeBSD will be treating it like a single (larger) device, not going through vinum or some other OS-level software RAID. I agree that your results are somewhat surprising.... -Chuck To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-stable" in the body of the message
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