From owner-freebsd-scsi Sun May 6 6:35:34 2001 Delivered-To: freebsd-scsi@freebsd.org Received: from hamilton.th.physik.uni-bonn.de (hamilton.th.physik.uni-bonn.de [131.220.162.85]) by hub.freebsd.org (Postfix) with ESMTP id 72C2937B423 for ; Sun, 6 May 2001 06:35:31 -0700 (PDT) (envelope-from conrad@th.physik.uni-bonn.de) Received: from merlin.th.physik.uni-bonn.de (merlin.th.physik.uni-bonn.de [131.220.161.121]) by hamilton.th.physik.uni-bonn.de (Postfix) with ESMTP id 6C9445D0E for ; Sun, 6 May 2001 15:35:30 +0200 (CEST) Received: by merlin.th.physik.uni-bonn.de (Postfix, from userid 145) id 0D1843640E; Sun, 6 May 2001 15:35:29 +0200 (CEST) Received: from localhost (localhost [127.0.0.1]) by merlin.th.physik.uni-bonn.de (Postfix) with ESMTP id F2B7A3260E for ; Sun, 6 May 2001 15:35:29 +0200 (CEST) Date: Sun, 6 May 2001 15:35:29 +0200 (CEST) From: Jan Conrad To: Subject: Write Cacheing on SCSI controllers? Message-ID: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-freebsd-scsi@FreeBSD.ORG Precedence: bulk X-Loop: FreeBSD.org Hi, I am setting up a new file server right now so I have some time to play around setting WCE on or off. To my surprise it did'nt matter that much! Just dd'ing 400MB of zeros to the disc gives me about 32MB/s, (nearly) no matter how WCE is set. (29160, IBM DDYS-T18350N) (softupdates on/off does'nt matter that much either...) This is in sharp contrast to ATA disks, where the write throughput drops by a factor of 3 when disabling WC. Is it possible that the SCSI controller does the write cacheing, compensating for the drive not doing it? regards Jan -- Physikalisches Institut der Universitaet Bonn Nussallee 12 D-53115 Bonn GERMANY To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-scsi" in the body of the message