Date: Wed, 20 May 1998 14:19:06 -0400 (EDT) From: Simon Shapiro <shimon@simon-shapiro.org> To: Raul Zighelboim <rzig@verio.net> Cc: "n@nectar.com" <n@nectar.com>, "scsi@freebsd.org" <scsi@FreeBSD.ORG>, Tom <tom@sdf.com> Subject: RE: DPT driver performance Message-ID: <XFMail.980520141906.shimon@simon-shapiro.org> In-Reply-To: <A03CD00C69B1D01195AB00A024ECEB1684CB26@kaori.communique.net>
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On 30-Apr-98 Raul Zighelboim wrote: > > I am running ONE drive on an AHC controller and ONE drive on a DPT > controller. No stripping, no raid. Just one drive. Both are formated > with 512b/s. > > No, I do not intend to run iozone as my main application. But it > bothers me that under the same conditions, the Adaptec controller can > write a large file twice as fast. > > You're saying that this is not relevant ? What you see is normal. Consider that the DPT has its own CPU, O/S, and SCSI controller chip. There are certain operations in which the latencies (as minute as they may be) introduced here are visible. The AHC controllers are directly attached to the system bus. If you intend to run only a single drive, on a desktop, I would say that a DPT is a costly and ineffective solution. If your needs are for RAID arrays, large disk farms, very heavy concurrent load, the DPT will serve you rather well. When testing/certifying a new driver release, I never use any of the standard benchmarks, for a reason; They are mostly geared towards sequential access to large files. Most of the DPTs are used in a heavily random seek environment or in a ``cannot fail'' environment. For these, I use my own mad testing procedure, which has been posted here more than once. I apologize for the late reply, but today is the second day since my move and the first in which I read email. Simon To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-scsi" in the body of the message
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