From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Greaves Subject: Re: removed disk && md-device Date: Thu, 10 May 2007 15:33:47 +0100 Message-ID: <46432D4B.4010302@dgreaves.com> References: <200705091417.09033.bs@q-leap.de> <20070509131450.GA31985@lapse.madduck.net> <200705091539.53863.bs@q-leap.de> <17986.50678.340484.891578@notabene.brown> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <17986.50678.340484.891578@notabene.brown> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: linux-hotplug-devel-bounces@lists.sourceforge.net Errors-To: linux-hotplug-devel-bounces@lists.sourceforge.net To: Neil Brown Cc: linux-raid@vger.kernel.org, 416512@bugs.debian.org, linux-hotplug-devel@lists.sourceforge.net List-Id: linux-raid.ids Neil Brown wrote: > On Wednesday May 9, bs@q-leap.de wrote: >> Neil Brown [2007.04.02.0953 +0200]: >>> Hmmm... this is somewhat awkward. You could argue that udev should be >>> taught to remove the device from the array before removing the device >> >from /dev. But I'm not convinced that you always want to 'fail' the >>> device. It is possible in this case that the array is quiescent and >>> you might like to shut it down without registering a device failure... >> Hmm, the the kernel advised hotplug to remove the device from /dev, but you >> don't want to remove it from md? Do you have an example for that case? > > Until there is known to be an inconsistency among the devices in an > array, you don't want to record that there is. > > Suppose I have two USB drives with a mounted but quiescent filesystem > on a raid1 across them. > I pull them both out, one after the other, to take them to my friends > place. > > I plug them both in and find that the array is degraded, because as > soon as I unplugged on, the other was told that it was now the only > one. And, in truth, so it was. Who updated the event count though? > Not good. Best to wait for an IO request that actually returns an > errors. Ah, now would that be a good time to update the event count? Maybe you should allow drives to be removed even if they aren't faulty or spare? A write to a removed device would mark it faulty in the other devices without waiting for a timeout. But joggling a usb stick (similar to your use case) would probably be OK since it would be hot-removed and then hot-added. David ------------------------------------------------------------------------- This SF.net email is sponsored by DB2 Express Download DB2 Express C - the FREE version of DB2 express and take control of your XML. No limits. Just data. Click to get it now. http://sourceforge.net/powerbar/db2/