Date: Fri, 24 Sep 2004 09:55:53 +0200 From: Pawel Jakub Dawidek <pjd@FreeBSD.org> To: Paul Mather <paul@gromit.dlib.vt.edu> Cc: freebsd-geom@freebsd.org Subject: Re: gstripe stripe size units? Message-ID: <20040924075553.GE9550@darkness.comp.waw.pl> In-Reply-To: <1095993821.5665.124.camel@zappa.Chelsea-Ct.Org> References: <1095993821.5665.124.camel@zappa.Chelsea-Ct.Org>
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--i3lJ51RuaGWuFYNw Content-Type: text/plain; charset=iso-8859-2 Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Thu, Sep 23, 2004 at 10:43:42PM -0400, Paul Mather wrote: +> What are the units for the stripe size argument to gstripe's "-s" +> option? E.g., does "gstripe label -s 4096 ..." mean use a stripe size +> of 4096 bytes; 4096 512-byte blocks; or what? The man page isn't +> specific. Bytes. +> What is a good suggested value for stripe size? Does anyone have any +> empirical results to share? Does it make sense to split the file system +> block size over the providers of the stripe when calculating the stripe +> size to use? E.g., for a 16 KB block size over two providers, make the +> stripe size 8 KB. Or, is geom_stripe I/O done in much larger transfers? +> (Usually, small transfers are poor for performance, arguing in favour of +> a larger, rather than smaller, stripe size.) The best you can do is to just try it. There is a tool for this, which I wrote for tests like this: src/tools/tools/raidtest/. If gstripe is running in "fast" mode (kern.geom.stripe.fast=3D1), size of stripe could be small, because then, it still sends as large I/O requests as possible and reorganize the data in memory, but this method consumes a lot of memory if you want it to be efficient. --=20 Pawel Jakub Dawidek http://www.FreeBSD.org pjd@FreeBSD.org http://garage.freebsd.pl FreeBSD committer Am I Evil? Yes, I Am! --i3lJ51RuaGWuFYNw Content-Type: application/pgp-signature Content-Disposition: inline -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.2.4 (FreeBSD) iD8DBQFBU9MJForvXbEpPzQRAoc8AKDsQvoWiUSJEYhNM/m/LY3Xz3bO1gCg7e+z P261sOYQADBHzz3cfA1Ybig= =OqiU -----END PGP SIGNATURE----- --i3lJ51RuaGWuFYNw--
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