The importance of narrow versus wide versus ultrawide f

[Herbert Wengatz]

+> > Date: Thu, 05 Sep 1996 01:19:43 +0200
+> > From: Alexandre Maret <ama...@infomaniak.ch>
+> > To: Bill Rockefeller <do...@netwizards.net>
+> > Cc: linux...@vger.rutgers.edu, linux...@vger.rutgers.edu
+> > Subject: Re: The importance of narrow versus wide versus ultrawide for raid (fwd)
+>
+> > Bill Rockefeller wrote:
+> > >
+> > > On Tue, 3 Sep 1996, Edward Welbon wrote:
+> > >
+> > > > Arachnid_Home_Page: http://www.bga.com/~welbon/spider
+> > > > Arachnid_Mail_List: arac...@bga.com
+> > > > Subliminal-Message: Run linux now
+> > > > MIME-Version: 1.0
+> > > > Content-Type: TEXT/PLAIN; charset=US-ASCII
+> > > > Sender: owner-li...@vger.rutgers.edu
+> > > > Precedence: bulk
+> > > >
+> > > > Any comments on how much effect of narrow versus wide versus ultrawide for
+> > > > raid. It appears that narrow drives are alot more availble and less
+> > > > expensive. How important is this?
+> >
+> > > IMHO I'd go with standard (read: CHEAP) SCSI-II Fast. We've got a great
+> > > SCSI-III (SCSI-II UW) here running off a Buslogic controller, and it
+> > > really doesn't seem to have enough performance benefit over SCSI-II to be
+> > > worth the extra bux. We've gone SCSI-III and we're stick with it, as
+> > > we've invested a nice chunk of money, but I'd recommend SCSI-II Fast
+> > <snip>
+> >
+> > BTW, 50MBps for data acquisition + 50 MBps out for storage = 100MBps
+> > total
+> > bandwidth... and if I'm right, 32bits PCI is 133MB/s... with some
+> > overhead
+> > (like downloading code into the NCR host adapter), you'll be near the
+> > max
+> > bus speed !
+> >
+> > alex
+> >
+> According to Seagate's specs, the data rate (internal) is around 75
+> to 120 megabits per second. This converts to a 9.375 to 15 megabytes
+> per second max sustained rate from the drive (this is for the
+> barrcuda 4lp drive family). So to get a 50mb/s xfer rate, you need a
+> raid solution with 6 drives to get your 50 mb/s (min) rate.

OK. Now tell me, which SCSI-Hostadapter is able to perform at 50 MB/s ?

Currently - None. (OK. Maybe some very exclusive ones... ;-) )

Ultra-Wide Adapters perform at a maximum of 40 MB/s - you can't get higher
with them. - The only way to reach higher performance is, to add another
adapter to have a combined speed.

Just adding disks is only the half truth. And you have to take into account
the overhead from the MD-Software under Linux. - Except you use a controller
which has Hardware-RAID. :)

+>
+> Bob Grabau
+> rgr...@darkstar.microserve.com
+> Linux - The choice for a GNU generation.

Regards,

Herbert

_____________________________________________________________________
Herbert Wengatz, 81375 Munich |Disclaim: This Mail is my own opinion,
Office :h...@uebemc.siemens.de |not that of my company.
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