Date: Sat, 16 Oct 1999 16:00:33 +0200 (MET DST) From: Gerard Roudier <groudier@club-internet.fr> To: Geoff Buckingham <geoffb@chuggalug.clues.com> Cc: Randell Jesup <rjesup@wgate.com>, scsi@FreeBSD.ORG, Mike Sinz <Michael@sinz.org> Subject: Re: FreeBSD 3.2 / Slow SCSI Dell PowerEdge 4300 Message-ID: <Pine.LNX.3.95.991016154328.770B-100000@localhost> In-Reply-To: <19991016005311.C56536@chuggalug.clues.com>
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On Sat, 16 Oct 1999, Geoff Buckingham wrote: > On Fri, Oct 15, 1999 at 07:14:15PM +0000, Randell Jesup wrote: > > =09Looking at the bonnie results from 10398: > >=20 > > write cache enabled > > -------Sequential Output-------- ---Sequential Input-- --= Random-- > > -Per Char- --Block--- -Rewrite-- -Per Char- --Block--- --= Seeks--- > > MB K/sec %CPU K/sec %CPU K/sec %CPU K/sec %CPU K/sec %CPU /= sec %CPU > > Number of Tags > > NO 100 7222 89.2 6801 21.8 2347 8.5 7330 93.3 7368 14.6 22= 6.5 4.7 > > 2 100 7263 90.3 6357 20.3 2730 9.9 7025 90.5 7321 14.9 20= 9.4 4.6 > > 3 100 7115 88.1 6406 20.8 2289 8.9 7307 93.9 7335 15.0 21= 2.6 4.5 > > 4 100 7281 90.0 6204 20.8 2278 9.1 7267 93.7 7350 15.3 21= 7.6 4.8 > > 8 100 7236 89.7 6007 19.4 2284 8.7 7239 93.1 7374 14.9 21= 3.4 4.5 > > 16 100 6775 83.7 6110 19.5 2283 8.7 7239 93.1 7380 14.8 21= 7.8 4.8 > > 32 100 7265 89.9 4385 13.9 2274 8.7 7302 93.7 7324 14.5 21= 8.9 4.5 > > 64 100 6731 83.3 3038 9.8 2271 8.7 7337 94.6 7356 14.7 21= 3.6 4.4 >=20 > Having brough bonnie into this I must offer some words of caution. >=20 > Bonnie only has three seekers for the random seek test, which is potentia= ly > very different from a heavily loaded qmail/exim/apache box. Indeed. As I noted in some other posting, it seems there is some subtle side effect when tags are disabled that makes multithreaded IO-streams replaced by a succession of single-threaded IO-streams that may last seconds. Just thinking to disk IOs sorting + reading ahead at the same time let guess the reasons.=20 I also suggest to measure _interactivity_. No need to be overall faster if a user that download a large file, for example, can take precedence over another user that download a small file due to the IO scheduling policy performing mostly batching instead of multi-threaded IOs.=20 > Most machines nowdays have a lot of RAM so large testfiles need to be use= d > to minimise cacheing effects (I have allways used -s 1024 but this takes > some time :-) G=E9rard. To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-scsi" in the body of the message
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