From mboxrd@z Thu Jan 1 00:00:00 1970 From: Christoph Hellwig Subject: Re: How to track down abysmal performance ata - raid1 - crypto - vg/lv - xfs Date: Wed, 4 Aug 2010 05:21:22 -0400 Message-ID: <20100804092122.GA2998@infradead.org> References: <20100804073546.GA7494@comet.dominikbrodowski.net> <20100804085039.GA11671@infradead.org> <20100804091317.GA27779@isilmar-3.linta.de> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <20100804091317.GA27779@isilmar-3.linta.de> Sender: linux-raid-owner@vger.kernel.org To: Dominik Brodowski , Christoph Hellwig , linux-raid@vger.kernel.org, xfs@oss.sgi.com, linux-kernel@vger.kernel.org List-Id: linux-raid.ids On Wed, Aug 04, 2010 at 11:13:17AM +0200, Dominik Brodowski wrote: > > show these problems? > > No, 2.6.31 to 2.6.34 show similar behaviour. Ok, so it's been around for a while. Can you test the write speed of each individual device layer by doing a large read from it, using: dd if= of=/dev/null bs=8k iflag=direct where device starts with the /dev/sda* device, and goes up to the MD device, the dm-crypt device and the LV. And yes, it's safe to read from the device while it's otherwise mounted/used.