Date: Sun, 15 Mar 1998 20:30:09 -0500 From: Cory Kempf <ckempf@enigami.com> To: Raul Zighelboim <rzig@gulfsouth.verio.net>, "'shimon@simon-shapiro.org'" <shimon@simon-shapiro.org> Cc: "scsi@freebsd.org" <scsi@FreeBSD.ORG> Subject: RE: to raid or not to raid Message-ID: <v04003a27b1322c3fa095@[208.140.182.45]> In-Reply-To: <A03CD00C69B1D01195AB00A024ECEB167110DC@kaori.communique.net>
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At 19:44 -0500 98.03.15, Raul Zighelboim wrote: >My missing link is: > >Will a (7 drive array under raid 5) be faster than a sinlg larger drive >?... > Will it be as fast as a (5 drive raid 5 array) ? > As it stands, the question is meaningless: it depends on the drives and the controllers. In general though, the more drives, the more overhead. IME, two drives striped together (assuming the bus could handle the throughput) gave the best performace. Beyond two drives, the command overhead started to show up. I would expect that the 7 drive array would be slower than the 5 drive array. A pair of Cheetah drives, on either FC or UW SCSI will probably give optimal performance. RAID 5 will cost performance. Slower disks will seriously cost performance. More than two disks will cost performance. A single Cheetah will perform less well. Any other drive model (at the moment, tomorrow the answers will change :-) ) will cost performance. Slower controllers will cost performance. Doing the XORs in software (rather than hardware) may cost performance. +C -- Thinking of purchasing RAM from the Chip Merchant? Please read this first: <http://www.enigami.com/~ckempf/chipmerchant.html>; Cory Kempf Macintosh / Unix Consulting & Software Development ckempf@enigami.com <http://www.enigami.com/~ckempf/>; To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-scsi" in the body of the message
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