Date: Thu, 28 Apr 2005 08:59:07 -0700 (PDT) From: Arne "Wörner" <arne_woerner@yahoo.com> To: Eric Anderson <anderson@centtech.com> Cc: freebsd-performance@freebsd.org Subject: Re: Very low disk performance Highpoint 1820a Message-ID: <20050428155908.41481.qmail@web41201.mail.yahoo.com> In-Reply-To: <4270F648.5030501@centtech.com>
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--- Eric Anderson <anderson@centtech.com> wrote: > First, understand that RAID 5 is dependant on fast hardware to > performa > the XOR operations. A single disk without any RAID can easily > outperform a RAID array if the RAID array is on a 'slow' > controller. > The Highpoint controllers are not exactly high-end fast RAID > controllers, so ~50MB/s isn't too bad for that I would say. > Did you happen to try a vinum RAID5? How about a stripe? > Furthermore RAID-5 needs to read the parity block, before it can update that block, so that there are 2 disc transactions more, which could explain the better performance of a single disk, too? Or does the striping effect (inherent to RAID-5) compensate those 2 extra transactions (at least in case of sequential writes)? -Arne __________________________________________________ Do You Yahoo!? Tired of spam? Yahoo! Mail has the best spam protection around http://mail.yahoo.com
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