Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932204AbVL3PQE (ORCPT ); Fri, 30 Dec 2005 10:16:04 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S932209AbVL3PQE (ORCPT ); Fri, 30 Dec 2005 10:16:04 -0500 Received: from [81.2.110.250] ([81.2.110.250]:32682 "EHLO lxorguk.ukuu.org.uk") by vger.kernel.org with ESMTP id S932204AbVL3PQD (ORCPT ); Fri, 30 Dec 2005 10:16:03 -0500 Subject: Re: RAID controller safety From: Alan Cox To: Kenny Simpson Cc: linux kernel In-Reply-To: <20051229162935.67301.qmail@web34106.mail.mud.yahoo.com> References: <20051229162935.67301.qmail@web34106.mail.mud.yahoo.com> Content-Type: text/plain Content-Transfer-Encoding: 7bit Date: Fri, 30 Dec 2005 15:17:46 +0000 Message-Id: <1135955866.28365.10.camel@localhost.localdomain> Mime-Version: 1.0 X-Mailer: Evolution 2.2.3 (2.2.3-2.fc4) Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1367 Lines: 29 On Iau, 2005-12-29 at 08:29 -0800, Kenny Simpson wrote: > Specificly, I am looking at the Adaptec RAID controllers and their i2o drivers. I am told the > kernel's i2o driver lacks a strong guarantee on fsync, and so far am unable to determine if the > dpt_i2o driver also falls short in this reguard. Only dpt can tell you what their firmware actually does. The i2o core drivers use the following rules i2o_scsi issues SCSI commands and assumes they are pass through and that the firmware does not fake completions early (or if it does that it battery backs them). For the known hardware the i2o SCSI class interface is a pass through interface with the card cpu just doing protocol gunk and supervision i2o_block by default assumes the card is caching. It adopts write through mode if the controller has no battery, write back if it shows battery. This can be configured differently via ioctls including the ability to tune write through of large I/O's (to avoid cache thrashing), and to do write back with no battery backup for performance in cases where losing the data on a crash doesn't matter (eg swap) Alan - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/