From mboxrd@z Thu Jan 1 00:00:00 1970 From: Neil Brown Subject: Re: mismatch_cnt questions - how about raid10? Date: Mon, 12 Mar 2007 16:35:35 +1100 Message-ID: <17908.59047.688420.79050@notabene.brown> References: <17898.45673.573800.56474@notabene.brown> <17899.17901.429001.702653@notabene.brown> <45ED3CB1.8070003@rabbit.us> <17901.16476.282987.982971@notabene.brown> <45ED48DB.6030002@rabbit.us> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: message from Peter Rabbitson on Tuesday March 6 Sender: linux-raid-owner@vger.kernel.org To: Peter Rabbitson Cc: linux-raid@vger.kernel.org List-Id: linux-raid.ids On Tuesday March 6, rabbit@rabbit.us wrote: > > > > I see. So basically for those of us who want to run swap on raid 1 or > 10, and at the same time want to rely on mismatch_cnt for early problem > detection, the only option is to create a separate md device just for > the swap. Is this about right? Though it is less likely, a regular filesystem could still (I think) genuinely write different data to difference devices in a raid1/10. So relying on mismatch_cnt for early problem detection probably isn't really workable. And I think that if a drive is returning bad data without signalling an error, then you are very much into the 'late' side of problem detection. I see the 'check' and 'repair' functions mostly as valuable for the fact that they read every block and will trigger sleeping bad blocks early. If they every find a discrepancy, then it is either perfectly normal, or something seriously wrong that could have been wrong for a while.... NeilBrown