Date: Sun, 13 Jul 2003 14:42:21 +0930 From: Malcolm Kay <malcolm.kay@internode.on.net> To: Andrea Venturoli <ml.ventu@flashnet.it>, freebsd-questions@freebsd.org Subject: Re: vinum and hot-swapping Message-ID: <200307131442.21264.malcolm.kay@internode.on.net> In-Reply-To: <200307130245.h6D2j8HB000556@soth.ventu> References: <200307130245.h6D2j8HB000556@soth.ventu>
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On Sun, 13 Jul 2003 19:15, Andrea Venturoli wrote: > ** Reply to note from "Greg 'groggy' Lehey" <grog@freebsd.org> Sat, 12 = Jul > 2003 17:13:29 +0930 > > > The real performance penalty for RAID-5 is simply that writes require > > so much I/O. Expect 25% of the write performance of RAID-0. > > Ok, I must ask this: > Shouldn't SCSI system allow paralell writes on different disks? Physical writes yes. But how does the data get there? The SCSI bus (like any other) has a finite bandwidth. But maybe if you are very clever you can coax the SCSI bus into transmitting the same information to all disks in parallel. > If so, why so much penalty? Malcolm Kay
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