From owner-freebsd-scsi@FreeBSD.ORG Wed May 12 02:49:09 2004 Return-Path: Delivered-To: freebsd-scsi@freebsd.org Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id B132A16A4CF; Wed, 12 May 2004 02:49:09 -0700 (PDT) Received: from mail.errors.firstcallgroup.co.uk (mail.errors.firstcallgroup.co.uk [213.167.69.198]) by mx1.FreeBSD.org (Postfix) with ESMTP id 4CB5E43D39; Wed, 12 May 2004 02:49:09 -0700 (PDT) (envelope-from petefrench@keithprowse.com) Received: from smaug.rattatosk ([172.16.1.8]) by mail.errors.firstcallgroup.co.uk with esmtp (Exim 4.22) id 1BNqMN-000DTw-3g; Wed, 12 May 2004 10:49:07 +0100 Received: from [172.16.1.6] (helo=dilbert.firstcallgroup.co.uk) by smaug.rattatosk with esmtp (Exim 4.22) id 1BNqMM-0000QR-Si; Wed, 12 May 2004 10:49:06 +0100 Received: from petefrench by dilbert.firstcallgroup.co.uk with local (Exim 4.30; FreeBSD) id 1BNqMM-0002EO-Ry; Wed, 12 May 2004 10:49:06 +0100 To: schweikh@schweikhardt.net, scottl@freebsd.org In-Reply-To: <40A13F22.80505@freebsd.org> Message-Id: From: Pete French Date: Wed, 12 May 2004 10:49:06 +0100 cc: freebsd-scsi@freebsd.org Subject: Re: 2120S Stripe - abysmal performance X-BeenThere: freebsd-scsi@freebsd.org X-Mailman-Version: 2.1.1 Precedence: list List-Id: SCSI subsystem List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 12 May 2004 09:49:09 -0000 > Read caching should be turned off unless you have a very specific need > for it. Having it on is going to hurt sequential read performance by a > 2x factor. The only time is makes sense is when you have a relatively > small data set that gets read repeatedly, with few other reads mixed in. Interesting comment. Does that refer to this particular controller, to caches on RAID controllers in general, or to caches on the drives themselves ? -pete.