From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S265487AbTFSUos (ORCPT ); Thu, 19 Jun 2003 16:44:48 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S265526AbTFSUos (ORCPT ); Thu, 19 Jun 2003 16:44:48 -0400 Received: from mail.dt.E-Technik.Uni-Dortmund.DE ([129.217.163.1]:30218 "EHLO krusty.dt.e-technik.uni-dortmund.de") by vger.kernel.org with ESMTP id S265487AbTFSUoo (ORCPT ); Thu, 19 Jun 2003 16:44:44 -0400 Date: Thu, 19 Jun 2003 22:58:39 +0200 From: Matthias Andree To: Linux-Kernel mailing list Subject: Re: SCSI Write Cache Enable in 2.4.20? Message-ID: <20030619205839.GA11080@merlin.emma.line.org> Mail-Followup-To: Linux-Kernel mailing list References: <3EF1EB2E.8010702@pobox.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <3EF1EB2E.8010702@pobox.com> User-Agent: Mutt/1.5.4i Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Thu, 19 Jun 2003, Jeff Garzik wrote: > This sounds like a bug, either in an application, or in Linux kernel's > scsi disk implementation. > > Data is only guaranteed to be written onto disk following an > fsync(2)-like operation in the application. And in turn, it is the > Linux kernel's responsibility to ensure that such a flush is propagated > all the down to the low-level driver, in my opinion. Sophisticated I think file systems also have certain write ordering requirements to maintain on-disk consistency, these would also need to make sure the order is correct. AFAICS, SuSE have patched the reiserfs in their 2.4.20 kernel (8.2) to use write barriers (however deep these are anchored), but ext3 or xfs don't show related log entries at boot-up or mount time. Is this something that will be fixed in 2.6 or will 2.6 still require me to turn off the write cache? > hosts can have barriers, and "dumb" hosts can simply call the drive's > flush-cache / sync-cache command. -- Matthias Andree