From mboxrd@z Thu Jan 1 00:00:00 1970 From: pg@lxra2.for.sabi.co.UK (Peter Grandi) Subject: Re: Low resync throughput Date: Fri, 27 Dec 2013 12:22:02 +0000 Message-ID: <21181.28906.59447.146830@tree.ty.sabi.co.uk> References: <52BD152C.5050301@ubuntu.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <52BD152C.5050301@ubuntu.com> Sender: linux-raid-owner@vger.kernel.org To: Linux RAID List-Id: linux-raid.ids > I have been experimenting with setting up a raid array on 3 > new drives that are each capable of about 180 MB/s throughput. I guess that if this a rotating disk drive "capable" is intended here in the marketing sense of "cannot exceed". :-) > I have tried raid5 and raid10 in both offset and far layouts > using both 64k and 512k chunk sizes, and the resync speed > seems to always be significantly less than the throughput of a > single drive, even after I write 500,000 to sync_speed_max. > The fastest of the bunch was raid10 in far mode, at ~140 MB/s, > and the rest were around 110 MB/s. The output of 'iostats -dx 1' might be interesting. :-) Also as to RAID5 you might want to look at 'man mdadm' the paragraph beginning "When creating a RAID5 array".