Date: Wed, 1 May 1996 11:47:43 +0200 (MET DST) From: Luigi Rizzo <luigi@labinfo.iet.unipi.it> To: terry@lambert.org (Terry Lambert) Cc: msmith@atrad.adelaide.edu.au, koshy@india.hp.com, hackers@FreeBSD.ORG, current@FreeBSD.ORG Subject: Re: lmbench IDE anomaly Message-ID: <199605010947.LAA08814@labinfo.iet.unipi.it> In-Reply-To: <199604302033.NAA07754@phaeton.artisoft.com> from "Terry Lambert" at Apr 30, 96 01:33:01 pm
next in thread | previous in thread | raw e-mail | index | archive | help
> > That's about right. The SCSI disk gets the chance to sort the I/O to suit > > itself, optimising its performance. The IDE disk only gets to look at one > > transaction at a time, so it's at the mercy of the disksorting code in > > the operating system. I don't know that FreeBSD's disksort stuff is > > terribly wonderful, but I'd happily stand corrected. > > The disksort stuff is pessimal. Contact mday@elbereth.org for details. The original poster was doing a couple of lmdd from /dev/rwd0a, the raw device. Does disksort get in the way in this case ? BTW, running a number of dd on /dev/wd0a works *much* better, you get almost n times the bandwidth at least with up to 5 instances, what I tried. Luigi ==================================================================== Luigi Rizzo Dip. di Ingegneria dell'Informazione email: luigi@iet.unipi.it Universita' di Pisa tel: +39-50-568533 via Diotisalvi 2, 56126 PISA (Italy) fax: +39-50-568522 http://www.iet.unipi.it/~luigi/ ====================================================================
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?199605010947.LAA08814>