Date: Mon, 31 Mar 2003 08:43:32 +0930 From: Greg 'groggy' Lehey <grog@FreeBSD.org> To: Dag-Erling =?iso-8859-1?Q?Sm=F8rgrav?= <des@ofug.org> Cc: Lukas Ertl <l.ertl@univie.ac.at> Subject: Re: vinum performance Message-ID: <20030330231332.GE1861@wantadilla.lemis.com> In-Reply-To: <xzp8yuwj0o0.fsf@flood.ping.uio.no> References: <20030330125138.K23911@leelou.in.tern> <xzpk7ehhxaf.fsf@flood.ping.uio.no> <20030330081831.5c4e317e.fearow@attbi.com> <xzpbrzthqpy.fsf@flood.ping.uio.no> <20030330163238.X23911@leelou.in.tern> <xzp8yuwj0o0.fsf@flood.ping.uio.no>
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--HeFlAV5LIbMFYYuh Content-Type: text/plain; charset=us-ascii Content-Disposition: inline On Sunday, 30 March 2003 at 18:10:07 +0200, Dag-Erling Smrgrav wrote: > Lukas Ertl <l.ertl@univie.ac.at> writes: >> I'm currently testing with prime stripe sizes, but it doesn't seem to >> help. I additionally added "options AHC_ALLOW_MEMIO" to the kernel, and it >> has raised write performance in the single-disk case (although I'm not >> happy with that one either; I expected a disk on a U160 controller to pump >> out more than ~65MB/s). > > Does the data sheet for your disk indicate that it can in fact write > much faster than that? The speed at which data is actually written > to the media is much lower than the bus speed - the bus speed *has* > to be higher to accomodate multiple devices. You're touching on one of the real issues here. For optimum transfers, a plex needs large stripes. If you're only doing one transfer at a time (like bonnie does), you'll just pick on individual disks alternately, so the performance can't be much better than a single disk. Do a large number of simultaneous transfers and it will be a different story. Greg -- See complete headers for address and phone numbers --HeFlAV5LIbMFYYuh Content-Type: application/pgp-signature Content-Disposition: inline -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.2.0 (FreeBSD) iD8DBQE+h3ocIubykFB6QiMRAsa1AKCv2Y3zu2R0Jep4/738J9nQAM0ZqACfW5Mo GwTvsiI6KuaQaWPxIx2Jj2I= =PgcI -----END PGP SIGNATURE----- --HeFlAV5LIbMFYYuh--
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