Date: Tue, 17 Feb 2009 13:46:20 -0700 From: Scott Long <scottl@samsco.org> To: Bruce Evans <brde@optusnet.com.au> Cc: FreeBSD@FreeBSD.org, FreeBSD Current <freebsd-current@FreeBSD.org>, Stable <freebsd-stable@FreeBSD.org>, Gary Jennejohn <gary.jennejohn@freenet.de>, scsi@FreeBSD.org Subject: Re: HEADS UP: More CAM fixes. Message-ID: <499B221C.2050804@samsco.org> In-Reply-To: <20090218073542.E5200@delplex.bde.org> References: <499981AF.9030204@samsco.org> <20090217164203.4c586f48@ernst.jennejohn.org> <20090218073542.E5200@delplex.bde.org>
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Bruce Evans wrote: > On Tue, 17 Feb 2009, Gary Jennejohn wrote: > >> I tested this with an Adaptec 29160. I saw no real improvement in >> performance, but also no regressions. >> >> I suspect that the old disk I had attached just didn't have enough >> performance reserves to show an improvement. >> >> My test scenario was buildworld. Since /usr/src and /usr/obj were both >> on the one disk it got a pretty good workout. > ^^^^ low >> >> AMD64 X2 (2.5 GHz) with 4GB of RAM. > > Buildworld hardly uses the disk at all. It reads and writes a few hundred > MB. Ideally the i/o should go at disk speeds of 50-200MB/S and thus take > between 20 and 5 seconds. In practice, it will take a few more seconds. > physically but perhaps even less virtually due to parallelism. > > Bruce Yes, on modern machines, buildworld is bound almost completely by disk latency, and not at all by disk or controller bandwidth. Scott
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