From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Alan D. Brunelle" Subject: Re: write is faster whan seek? Date: Wed, 11 Jun 2008 07:52:11 -0400 Message-ID: <484FBC6B.3080703@hp.com> References: <484FB92D.4090808@hp.com> <20080611114950.GW20851@kernel.dk> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Cc: Dmitri Monakhov , linux-fsdevel@vger.kernel.org To: Jens Axboe Return-path: Received: from g5t0008.atlanta.hp.com ([15.192.0.45]:36056 "EHLO g5t0008.atlanta.hp.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751163AbYFKLwP (ORCPT ); Wed, 11 Jun 2008 07:52:15 -0400 In-Reply-To: <20080611114950.GW20851@kernel.dk> Sender: linux-fsdevel-owner@vger.kernel.org List-ID: Jens Axboe wrote: > On Wed, Jun 11 2008, Alan D. Brunelle wrote: >> Dmitri Monakhov wrote: >> >> Could it be that in the first case you will have merges, thus creating >> fewer/larger I/O requests? Running iostat -x during the two runs, and >> watching the output is a good first place to start. > > I think it's mostly down to whether a specific drive is good at doing > 124kb writes + 4k seek (and repeat) compared to regular streaming > writes. The tested disk was SATA with write back caching, there should > be no real command overhead gain in those size ranges. > Probably true, I'd think the iostat -x data would be very helpful though.