Date: Sat, 25 Sep 2004 16:52:36 +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: <20040925145236.GO9550@darkness.comp.waw.pl> In-Reply-To: <1096062713.9306.119.camel@zappa.Chelsea-Ct.Org> References: <1095993821.5665.124.camel@zappa.Chelsea-Ct.Org> <20040924075553.GE9550@darkness.comp.waw.pl> <1096062713.9306.119.camel@zappa.Chelsea-Ct.Org>
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--TRkqPRiqIDKgfg/F Content-Type: text/plain; charset=iso-8859-2 Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Fri, Sep 24, 2004 at 05:51:54PM -0400, Paul Mather wrote: +> > 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 reque= sts +> > as possible and reorganize the data in memory, but this method consumes +> > a lot of memory if you want it to be efficient. +>=20 +> One thing that puzzles me is that no matter how large I made the stripe +> size, I never got a kern.geom.stripe.fast_failed > 0. [...] It will be hard for raidtest tests, but it is really easy for UFS+softupdates and small stripe size. +> I'm puzzled because a stripe of 16 MB will not fit in 6553600 bytes, so +> surely fast_failed should be > 0 at stripes of 8 MB or greater in my +> tests for the above value of kern.geom.stripe.maxmem? This is a problem for small stripe sizes, not for big ones. Remember, that no metter how large stripe size is, maximum I/O request size is still 128kB, so for stripe size >=3D 64kB there is not even chance to fail - gstripe don't allocate memory if it is not needed, i.e. if we can split request on two pieces or even send it as one piece. +> Also, I don't know what the distribution of request sizes is in +> raidtest.data. The raidtest program operates over the raw device, and +> so may not necessarily behave in terms of issuing requests as, say, a +> UFS filesystem might. Of course. You should run some file systems tests as well. --=20 Pawel Jakub Dawidek http://www.FreeBSD.org pjd@FreeBSD.org http://garage.freebsd.pl FreeBSD committer Am I Evil? Yes, I Am! --TRkqPRiqIDKgfg/F Content-Type: application/pgp-signature Content-Disposition: inline -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.2.4 (FreeBSD) iD8DBQFBVYY0ForvXbEpPzQRAqYcAJ9e5LXWgcpMI+P4usPwszlcfks7AwCeKehD PslUqk8dcrJ2ggUFGQNh6yE= =QiNi -----END PGP SIGNATURE----- --TRkqPRiqIDKgfg/F--
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