From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Grant Grundler" Subject: Re: weird throughput on write to SATA disk Date: Tue, 14 Oct 2008 09:09:21 -0700 Message-ID: References: <1223925629.3947.7.camel@duo> <1223932956.3947.22.camel@duo> <1223936351.3947.41.camel@duo> <1223975694.3947.77.camel@duo> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Return-path: Received: from smtp-out.google.com ([216.239.33.17]:7686 "EHLO smtp-out3.google.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1751046AbYJNQJi (ORCPT ); Tue, 14 Oct 2008 12:09:38 -0400 In-Reply-To: <1223975694.3947.77.camel@duo> Content-Disposition: inline Sender: linux-ide-owner@vger.kernel.org List-Id: linux-ide@vger.kernel.org To: kenneth johansson Cc: linux-ide@vger.kernel.org, linux-kernel@vger.kernel.org On Tue, Oct 14, 2008 at 2:14 AM, kenneth johansson wrote: ... > All my numbers comes from using 1MB blocks. but I'm not using dd. > After removing the logic that actually put some data into the buffers I > do get about 105 MB/sec using O_DIRECT. Ok. Good. > I'm doing a full disk write now to get a reference plot. See http://hdperf.sourceforge.net/ and http://nathan.laredo.name/hdperf/ Simple tool to (relatively) quickly measure the perf across the disk platter. > Not using O_DIRECT should be almost identical. *should* - but there are known problems with writeback. Some of them are described nicely by Dave Chinner as "Random Thought #3": http://iou.parisc-linux.org/lsf2008/linux_storage_scalability-Dave_Chinner.odp Look for "writeback" for a summary of the discussion: http://iou.parisc-linux.org/lsf2008/SUMMARY-Storage.txt hth, grant