From mboxrd@z Thu Jan 1 00:00:00 1970 From: Roger Heflin Subject: Re: RAID halting Date: Sat, 04 Apr 2009 07:38:28 -0500 Message-ID: <49D754C4.4010702@gmail.com> References: <20090404071250.NYQP28081.cdptpa-omta04.mail.rr.com@Leslie> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20090404071250.NYQP28081.cdptpa-omta04.mail.rr.com@Leslie> Sender: linux-raid-owner@vger.kernel.org To: lrhorer@satx.rr.com Cc: 'Linux RAID' List-Id: linux-raid.ids Lelsie Rhorer wrote: >> This sounds like a filesys problem rather than a RAID problem. > > I considered that. It may well be. > >> One thing that can cause this sort of behaviour is if the filesystem is in >> the middle of a sync and has to complete it before the create can >> complete, and the sync is writing out many megabytes of data. > > For between 40 seconds and 2 minutes? The drive subsystem can easily gulp > down 200 megabytes to 6000 megabytes in that period of time. What synch > would be that large? Secondly, the problem occurs also when there is > relatively little or no data being written to the array. Finally, unless I > am misunderstanding at what layers iostat and atop are reporting the > traffic, the fact all drive writes invariably fall to dead zero during an > event and reads on precisely half the drives (and always the same drives) > drop to dead zero suggests to me this is not the case. > > If you have things setup such that you have lights on the disks, and can check the lights when the event is happening, often if a single drive is being slow it will be the only one with its lights on when things are going bad.