From mboxrd@z Thu Jan 1 00:00:00 1970 From: Dieter Stueken Subject: Re: raid and sleeping bad sectors Date: Wed, 30 Jun 2004 10:44:44 +0200 Sender: linux-raid-owner@vger.kernel.org Message-ID: <40E27D7C.2040101@conterra.de> References: <200406300219.i5U2JW327038@watkins-home.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <200406300219.i5U2JW327038@watkins-home.com> To: 'linux-raid' List-Id: linux-raid.ids Guy wrote: > I don't think plan b needs to be handled as stated. If a cable is loose, > the amount of data that needs to be written somewhere else could be vast. > At least as big as 1 disk! agreed; any such "active" bad block replacement will only postpone the problem. It will never be able to solve the problem absolutely reliable. I also agree, that it makes the system more complex and may need some manual intervention, too. > That brings me back to: > If the hard drive can't re-locate the bad block, then, accept that you have > had a failure. completely true. Kick off the bad disk and rebuild a new one sound easy and save. But it is not! Before/during rebuild, your raid system runs unprotected in a very fragile state, even more fragile than a single disk system without raid! Thus the additional spare blocks may help to bridge over this phase more safely. Thus this is not an alternative of replacing the bad disk; you will do that, definitely! Instead it is just an addition. If you are hanging on a rope on a cliff, and notice, that the rope shows a defect, what will you do? Cut it off, before it breaks completely! and while falling, you may inspect your backpack to find a spare rope to use..... Dieter.