From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jens Axboe Subject: Re: write is faster whan seek? Date: Wed, 11 Jun 2008 13:49:54 +0200 Message-ID: <20080611114950.GW20851@kernel.dk> References: <484FB92D.4090808@hp.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Dmitri Monakhov , linux-fsdevel@vger.kernel.org To: "Alan D. Brunelle" Return-path: Received: from brick.kernel.dk ([87.55.233.238]:24679 "EHLO kernel.dk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750904AbYFKLt5 (ORCPT ); Wed, 11 Jun 2008 07:49:57 -0400 Content-Disposition: inline In-Reply-To: <484FB92D.4090808@hp.com> Sender: linux-fsdevel-owner@vger.kernel.org List-ID: 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. -- Jens Axboe