Date: Fri, 4 Apr 2003 15:41:35 +0930 From: Greg 'groggy' Lehey <grog@FreeBSD.org> To: Lukas Ertl <l.ertl@univie.ac.at> Cc: freebsd-stable@FreeBSD.org Subject: Re: vinum performance Message-ID: <20030404061135.GO60909@wantadilla.lemis.com> In-Reply-To: <20030402102225.Y19644@pcle2.cc.univie.ac.at> References: <20030330125138.K23911@leelou.in.tern> <20030330231000.GB1861@wantadilla.lemis.com> <20030401162820.E19644@pcle2.cc.univie.ac.at> <20030402001826.GU34617@wantadilla.lemis.com> <20030402102225.Y19644@pcle2.cc.univie.ac.at>
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--B3NBd8mrXZtPJEYR Content-Type: text/plain; charset=us-ascii Content-Disposition: inline On Wednesday, 2 April 2003 at 10:24:39 +0200, Lukas Ertl wrote: > On Wed, 2 Apr 2003, Greg 'groggy' Lehey wrote: > >>> I've done some rawio benchmarks with different process counts (1, 2, 4, 8, >>> 16, 32 and 64). The results are at >>> <http://mailbox.univie.ac.at/~le/rawio.html>. >> >> How does this compare to the raw disk? > > Oops, sorry, I've forgotten to include them on the page. They are on there > now. > > Raw disk performance is indeed worse than RAID0/RAID5. Yes, those figures look much more like what I would expect. Those RAID-0 figures look nice, don't they? > Also interesting is that the sequential read performance drops > significantly in all cases when going from 8 to 16 processes. Yes, that's strange. I wonder what causes it. > Probably the bus is filled up then. No, the various busses don't know how many processes are active. Looking at those figures, it's clear that there's some cache activity then. There's no way you can transfer 52 MB/s from a single disk platter, so it must be in cache. Somewhere between 8 and 16 concurrent transfers from different parts of the disk must confuse the cache. You'll notice that after that point, the read speeds pick up again. Another thing of interest is that there's a slight drop-off in some cases when going from 256 kB to 512 kB stripes. I've seen that elsewhere as well, but I still don't have a good explanation. I'd be interested to see how RAIDFrame compares. Greg -- See complete headers for address and phone numbers --B3NBd8mrXZtPJEYR Content-Type: application/pgp-signature Content-Disposition: inline -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.2.0 (FreeBSD) iD8DBQE+jSIXIubykFB6QiMRAovBAJ9SJD3+NxBgXoaaAX+D94NC7R6lwwCfZy7J 55WZ8VMJSdLh5LjRhubdM2Y= =U8Kg -----END PGP SIGNATURE----- --B3NBd8mrXZtPJEYR--
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