From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jens Axboe Subject: Re: Write cache on SATA drives? Date: Sat, 2 Jul 2005 09:07:55 +0200 Message-ID: <20050702070750.GL2243@suse.de> References: <20050701062416.GQ2243@suse.de> <20050701083308.GZ2243@suse.de> <20050701084717.GA18306@merlin.emma.line.org> <20050701085412.GA2243@suse.de> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Received: from ns.virtualhost.dk ([195.184.98.160]:41652 "EHLO virtualhost.dk") by vger.kernel.org with ESMTP id S261827AbVGBHG2 (ORCPT ); Sat, 2 Jul 2005 03:06:28 -0400 Content-Disposition: inline In-Reply-To: Sender: linux-scsi-owner@vger.kernel.org List-Id: linux-scsi@vger.kernel.org To: Matthias Andree Cc: "Edwards, Scott (GE Healthcare)" , linux-scsi@vger.kernel.org On Sat, Jul 02 2005, Matthias Andree wrote: > Jens Axboe writes: > > >> I'm not acquainted with kernel/block I/O queueing internals. > > > > SCSI without TCQ or with TCQ depth=1 should be safe, provided the driver > > never reorders a command once it has received it. > > Wouldn't we rather use *deep* TCQ and set write cache enable to 0 then? Depends, if you can't use ordered tags it wont help you. > Does anybody have benchmarks with TCQ depth = 1/WCE = 1 vs. TCQ = > (64+)/WCE = 0? I only have ancient SCSI drives in test machines, so my > testing wouldn't be representative. I posted some for NCQ, see lkml/linux-ide. > >> > > 2. for traditional IDE (such as VIA 82*, PIIX_*)? > >> > > >> > In SUSE kernels, for many years. Since 2.6.7/8'ish in Linus' kernels. > >> > >> I don't care for vendor kernels. Is listing 2.6.8 safe? > > > > Check the changelogs, I can't remember exactly if it was 2.6.7 or 2.6.8 > > (or perhaps .6...). > > Hm. Any buzz^Wkeywords to look for? "barrier" doesn't seem to be the > right word, it yields only memory barriers and an as-iosched fix in > 2.6.7. I checked ChangeLog-2.6.[56789]. Grep for blk_queue_ordered or similar in the patch. -- Jens Axboe