From owner-freebsd-scsi Thu Sep 21 4:48:55 2000 Delivered-To: freebsd-scsi@freebsd.org Received: from mail-relay.eunet.no (mail-relay.eunet.no [193.71.71.242]) by hub.freebsd.org (Postfix) with ESMTP id 7C34F37B42C; Thu, 21 Sep 2000 04:48:51 -0700 (PDT) Received: from login-1.eunet.no (login-1.eunet.no [193.75.110.2]) by mail-relay.eunet.no (8.9.3/8.9.3/GN) with ESMTP id NAA58037; Thu, 21 Sep 2000 13:48:49 +0200 (CEST) (envelope-from mbendiks@eunet.no) Received: from localhost (mbendiks@localhost) by login-1.eunet.no (8.9.3/8.8.8) with ESMTP id NAA38177; Thu, 21 Sep 2000 13:48:49 +0200 (CEST) (envelope-from mbendiks@eunet.no) X-Authentication-Warning: login-1.eunet.no: mbendiks owned process doing -bs Date: Thu, 21 Sep 2000 13:48:49 +0200 (CEST) From: Marius Bendiksen To: Stephen Byan Cc: fs@FreeBSD.ORG, sos@FreeBSD.ORG, "'freeBSD-scsi@freeBSD.org'" Subject: RE: disable write caching with softupdates? In-Reply-To: <8133266FE373D11190CD00805FA768BF055BD1C9@shrcmsg1.tdh.qntm.com> 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 > Wouldn't it be acceptable to mark the meta-data writes as non-cacheable > (i.e. write though to the media before signalling completion), and let the > remaining writes (user data writes) be cacheable? I think this would improve > the performance of the file system. Actually, performance-wise, you'd probably want to know the real geometry, given all the stuff FFS does to exploit it. > SCSI has supported this for years, in the form of the FUA bit in the CDB for > the write command. Somewhat similar behavior can be had in the newer flavors As I recall, and from what Eivind noted, this bit is routinely ignored in about 90% of all drives out there. > of ATA by issuing a "flush cache" command after each meta-data write, and > waiting until the flush command completes before signalling the completion > of the non-cacheable write. This has the potential for degrading performance even further. I think you would prefer to disable cache over this. Marius To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-scsi" in the body of the message