From owner-freebsd-questions@FreeBSD.ORG Tue Feb 20 15:59:54 2007 Return-Path: X-Original-To: freebsd-questions@freebsd.org Delivered-To: freebsd-questions@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [69.147.83.52]) by hub.freebsd.org (Postfix) with ESMTP id D636816AA14 for ; Tue, 20 Feb 2007 15:59:54 +0000 (UTC) (envelope-from kirk@strauser.com) Received: from kanga.honeypot.net (kanga.honeypot.net [208.162.254.122]) by mx1.freebsd.org (Postfix) with ESMTP id 5F89A13C4B2 for ; Tue, 20 Feb 2007 15:59:54 +0000 (UTC) (envelope-from kirk@strauser.com) Received: from localhost (localhost [127.0.0.1]) by kanga.honeypot.net (Postfix) with ESMTP id A7B7B20B40B for ; Tue, 20 Feb 2007 09:59:53 -0600 (CST) X-Virus-Scanned: amavisd-new at honeypot.net Received: from kanga.honeypot.net ([127.0.0.1]) by localhost (kanga.honeypot.net [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id hhB3xbPXQbey for ; Tue, 20 Feb 2007 09:59:50 -0600 (CST) Received: from janus.daycos.com (janus.daycos.com [10.45.12.2]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by kanga.honeypot.net (Postfix) with ESMTP id 52B1A20B403 for ; Tue, 20 Feb 2007 09:59:50 -0600 (CST) From: Kirk Strauser To: freebsd-questions@freebsd.org Date: Tue, 20 Feb 2007 09:59:44 -0600 User-Agent: KMail/1.9.6 X-Face: T+/_{qmjgbosI0J/e83I~w[&VF'w)!((xEpj///^bA/6?jHHS?nq+T8_+`nh"WnEWCWG, \}]Y2$)) =?utf-8?q?vLVz4ACChrEcb=7DCO=5EtYmMG=5C=0A=09ts=2Em=3F=5B7=5B6OwE*dAJ*9f+m?= =?utf-8?q?X=2E7R32qeN=5EDJ=5C?=(k@evW?IRQCy.^ MIME-Version: 1.0 Content-Type: multipart/signed; boundary="nextPart3698685.sf1xxLde7l"; protocol="application/pgp-signature"; micalg=pgp-sha1 Content-Transfer-Encoding: 7bit Message-Id: <200702200959.48154.kirk@strauser.com> Subject: Deciphering camcontrol - is prefetch enabled? X-BeenThere: freebsd-questions@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: User questions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Tue, 20 Feb 2007 15:59:54 -0000 --nextPart3698685.sf1xxLde7l Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: quoted-printable Content-Disposition: inline I have a new set of SCSI drives, all like: da2 at mpt0 bus 0 target 3 lun 0 da2: Fixed Direct Access SCSI-3 device da2: 320.000MB/s transfers (160.000MHz, offset 63, 16bit), Tagged Queue= ing Enabled da2: 35003MB (71687372 512 byte sectors: 255H 63S/T 4462C) =46rom what I can tell, the only way to adjust parameters on SCSI drives is through camcontrol's modepage option. The output on one of the new disks looks like: $ sudo camcontrol modepage 0:2 -m 8 IC: 0 ABPF: 0 CAP: 0 DISC: 1 SIZE: 0 WCE: 1 MF: 0 RCD: 0 Demand Retention Priority: 0 Write Retention Priority: 0 Disable Pre-fetch Transfer Length: 65535 Minimum Pre-fetch: 0 Maximum Pre-fetch: 65535 Maximum Pre-fetch Ceiling: 65535 I'm pretty sure that "WCE" means "write cache enabled", which is what we want. However, I'm pretty sure I want to enable prefetching, too, since data access on them will often involve a set of concurrent long streaming reads. In that case, wouldn't prefetch reduce contention among the read processes? If so, from looking at the above output, does it seem to be enabled? Since I left my handy "Cryptic SCSI Acronym Dictionary" elsewhere, I don't have any idea what the above is actually trying to tell me. =2D-=20 Kirk Strauser --nextPart3698685.sf1xxLde7l Content-Type: application/pgp-signature -----BEGIN PGP SIGNATURE----- iD8DBQBF2xr05sRg+Y0CpvERAorkAJwKo8BoLsNgQjaCifdAy5KmydB9QACaAg99 jDs1KqtYLF8dFVGQz2NGl8s= =xmQ8 -----END PGP SIGNATURE----- --nextPart3698685.sf1xxLde7l--