Path: utzoo!attcan!uunet!cs.utexas.edu!swrinde!emory!mephisto!mcnc!rti!xyzzy!goudreau
From: goudreau@dg-rtp.dg.com (Bob Goudreau)
Newsgroups: comp.unix.wizards
Subject: Re: mirrored file systems
Message-ID: <47@xyzzy.UUCP>
Date: 13 Feb 90 21:32:48 GMT
References: <11071@encore.Encore.COM> <4812@amelia.nas.nasa.gov> <11083@encore.Encore.COM> <605@bbxsda.UUCP> <4849@amelia.nas.nasa.gov> <17902@rpp386.cactus.org> <4882@amelia.nas.nasa.gov>
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Reply-To: goudreau@larrybud.dg.com (Bob Goudreau)
Organization: Data General Corporation, Research Triangle Park, NC
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In article <4882@amelia.nas.nasa.gov> truesdel@sun217..nas.nasa.gov (David A. Truesdell) writes:
>In addition, a mirrored filesystem won't help your I/O throughput.

Actually, that depends on the system's read/write ratio.  Writes to
a mirrored file system obviously must result in I/O to each (valid)
side of the mirror.  But reads, on the other hand, only need to
find *one* good copy.  An intelligently implemented mirrored file
system can increase I/O throughput by distributing read requests
evenly among the copies, thus leaving the unused sides of the
mirror free to service other incoming read requests.

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