From mboxrd@z Thu Jan 1 00:00:00 1970 From: Neil Brown Subject: Re: Slow raid10 resync Date: Wed, 24 Jun 2009 13:19:24 +1000 Message-ID: <19009.39740.60091.349944@notabene.brown> References: <2A22ECE278A6604A84476172F106BFCE07AC7A5A@CORPUSMX50A.corp.emc.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: message from Ryan_MichaelS@emc.com on Monday June 22 Sender: linux-raid-owner@vger.kernel.org To: Ryan_MichaelS@emc.com Cc: linux-raid@vger.kernel.org List-Id: linux-raid.ids On Monday June 22, Ryan_MichaelS@emc.com wrote: > Occasionally one of my devices with a 4 drive raid10 array resyncs very > slowly. Typical resync speed is in the 50-60 MB/sec range. When > running slow the speed is around 7-10 MB/sec. sync_speed_min is set to > 20,000, max is set to 200,000. By setting sync_speed_min to 5000 I can > slow the sync further, but setting it back to 20000 doesn't fix the > speed. Other IO on the system is normal. The drives and the CPU are > not maxed. > > I don't know what is triggering this slow sync state. Once in this > state it will continue until the build completes. > > Any idea what might be happening here? I'm running Debian with a 2.6.22 > kernel. Not really... There have been a couple of bugs that cause resync to go faster than it should, but I can't think of anything that would make it go slower than sync_speed_min unless that the the fastest that the storage subsystem could handle. Is this just a default raid10 with 'near=2' as the layout? NeilBrown