From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jens Axboe Subject: Re: [PATCH 00/33] SG table chaining support Date: Mon, 16 Jul 2007 18:43:10 +0200 Message-ID: <20070716164309.GA5195@kernel.dk> References: <11845792671245-git-send-email-jens.axboe@oracle.com> <18075.31515.974905.507754@stoffel.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Received: from brick.kernel.dk ([80.160.20.94]:12070 "EHLO kernel.dk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1760284AbXGPQnu (ORCPT ); Mon, 16 Jul 2007 12:43:50 -0400 Content-Disposition: inline In-Reply-To: Sender: linux-scsi-owner@vger.kernel.org List-Id: linux-scsi@vger.kernel.org To: Kai Makisara Cc: "Martin K. Petersen" , John Stoffel , linux-kernel@vger.kernel.org, linux-scsi@vger.kernel.org On Mon, Jul 16 2007, Kai Makisara wrote: > On Mon, 16 Jul 2007, Martin K. Petersen wrote: > > > >>>>> "John" == John Stoffel writes: > > > > John> Will this help out tape drive performance at all? I looked > > John> through the patches quickly, esp the AIC7xxx stuff since that's > > John> what I use, but nothing jumped out at me... > > > > Yes. Most modern tape drives want a block size of 1MB or higher. > > With the old stack we'd be stuck at 512KB because the sg limitations > > caused us to come just short of 1MB... > > > Tape block sizes up to 16 MB have been possible for a very long time but > this has required tuning of the block/scsi parameters. Very few people > seem to have done this and the common (mis)belief seems to be that the > tape block size limit has been 512 kB. It is good if this tuning is not > needed in future. The main difference is now you get to do it without hacks and in a clean way, so it works through the normal IO path and not some on-the-side thing (or st only). -- Jens Axboe