From mboxrd@z Thu Jan 1 00:00:00 1970 From: "NeilBrown" Subject: Re: unbelievably bad performance: 2.6.27.37 and raid6 Date: Mon, 2 Nov 2009 10:43:49 +1100 Message-ID: References: <200910311243.35126.tfjellstrom@shaw.ca> <4AEDE38F.3080408@gmail.com> <200911011241.40735.tfjellstrom@shaw.ca> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7BIT Return-path: In-Reply-To: <200911011241.40735.tfjellstrom@shaw.ca> Sender: linux-raid-owner@vger.kernel.org To: tfjellstrom@shaw.ca Cc: Andrew Dunn , Jon Nelson , LinuxRaid , pernegger@gmail.com List-Id: linux-raid.ids On Mon, November 2, 2009 6:41 am, Thomas Fjellstrom wrote: > On Sun November 1 2009, Andrew Dunn wrote: >> Are we to expect some resolution in newer kernels? > > I assume all of the new per-bdi-writeback work going on in .33+ will have > a > large impact. At least I'm hoping. > >> I am going to rebuild my array (backup data and re-create) to modify the >> chunk size this week. I hope to get a much higher performance when >> increasing from 64k chunk size to 1024k. >> >> Is there a way to modify chunk size in place or does the array need to >> be re-created? > > This I'm not sure about. I'd like to be able to reshape to a new chunk > size > for testing. Reshaping to a new chunksize is possible with the latest mdadm and kernel, but I would recommend waiting for mdadm-3.1.1 and 2.6.32. With the current code, a device failure during reshape followed by an unclean shutdown while reshape is happening can lead to unrecoverable data loss. Even a clean shutdown before the shape finishes in that case might be a problem. NeilBrown