From mboxrd@z Thu Jan 1 00:00:00 1970 From: Neil Brown Subject: Re: Zeroing multiple superblocks Date: Fri, 29 Jan 2010 23:31:11 +1100 Message-ID: <20100129233111.5c9cc1d0@notabene> References: <20100122200924.GA29183@psychosis.jim.sh> <20100125095221.GV21495@skl-net.de> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20100125095221.GV21495@skl-net.de> Sender: linux-raid-owner@vger.kernel.org To: Andre Noll Cc: Jim Paris , linux-raid@vger.kernel.org List-Id: linux-raid.ids On Mon, 25 Jan 2010 10:52:21 +0100 Andre Noll wrote: > On 15:09, Jim Paris wrote: > > > I guess the only way to be fully safe with the current approach is to > > do a zero-superblock over and over until it complains. > > mdadm --zero-superblock tries to guess the location of the superblock. > If more than one superblock is found, the one with the latest creation > time is being zeroed. So yes, the method you describe works and I think > it is the most reliable way to remove all superblocks of a device. > > Maybe we could teach mdadm --zero-superblock to honor the --metadata=x > option which would zero-out the region of the device where the > version-x superblock is located. Latest mdadm has this feature. And if --metadata= isn't given, it repeatedly trying to find and zero a superblock until no more superblocks can be found. NeilBrown