Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932257AbVL3QSJ (ORCPT ); Fri, 30 Dec 2005 11:18:09 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S932261AbVL3QSI (ORCPT ); Fri, 30 Dec 2005 11:18:08 -0500 Received: from web34110.mail.mud.yahoo.com ([66.163.178.108]:38259 "HELO web34110.mail.mud.yahoo.com") by vger.kernel.org with SMTP id S932257AbVL3QSG (ORCPT ); Fri, 30 Dec 2005 11:18:06 -0500 DomainKey-Signature: a=rsa-sha1; q=dns; c=nofws; s=s1024; d=yahoo.com; h=Message-ID:Received:Date:From:Subject:To:Cc:In-Reply-To:MIME-Version:Content-Type:Content-Transfer-Encoding; b=gB8jWJgpI2QjLZBVZmdxBqLXiOFAlf9+mFOETk/erjaCpl0vBMWCm7xOq2sNaRSC4BFujPwTnrqUvz8mNwCSsewBHmBQkNdXUDhh+rDBaeKJp8hZLpdyYq5sRrPNnhkA+rE5D2qc2JE0ZGx20+P6PRdQg74irXg9KwdST5e7ZN0= ; Message-ID: <20051230161805.64631.qmail@web34110.mail.mud.yahoo.com> Date: Fri, 30 Dec 2005 08:18:05 -0800 (PST) From: Kenny Simpson Subject: Re: RAID controller safety To: Alan Cox Cc: linux kernel In-Reply-To: <1135955866.28365.10.camel@localhost.localdomain> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7BIT Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1855 Lines: 44 > > 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. Yeah, I wasn't so much interrested in the firmware just yet, just interrested if the device driver (dpt_i2o) gave it a fighting chance of doing the right thing. > The i2o core drivers use the following rules > 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) That's what I read in the comments too, but looking at the code I only ever see it set to write-back. I verified this with blktool - our controllers have no battery, and blktool showed the i2o-wcache state as write-back. However, I was also told that the i2o_block driver lacks barrier support, so even in the write-back case, the controller won't be told to flush/sync. I was sent a patch against 2.6.10 that implements barrier support in i2o_block, but the code base has shifted too much for me to make it apply. -Kenny __________________________________ Yahoo! for Good - Make a difference this year. http://brand.yahoo.com/cybergivingweek2005/ - 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/