From mboxrd@z Thu Jan 1 00:00:00 1970 From: Paul Clements Subject: Re: [PATCH] md: fix device size calculation with non-persistent superblock Date: Tue, 24 Feb 2004 10:27:55 -0500 Sender: linux-raid-owner@vger.kernel.org Message-ID: <403B6D7B.29A4B2A0@SteelEye.com> References: <20040223024124.GA1590@psilocybus> <16441.33071.218049.163976@notabene.cse.unsw.edu.au> <403A30F9.D54AAC68@SteelEye.com> <16442.42303.445148.394516@notabene.cse.unsw.edu.au> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Return-path: To: Neil Brown Cc: linux-raid@vger.kernel.org List-Id: linux-raid.ids Neil Brown wrote: > > On Monday February 23, Paul.Clements@SteelEye.com wrote: > > Neil, > > > > Currently, the device size calculation is not correct when hot-adding > > devices to arrays with non-persistent superblocks. Device size is always > > calculated as if there were a physical superblock on every device. The > > attached simple change to hot_add_disk() fixes the problem. > > Hmm.. I had always assumed that non-persistent superblocks only worked > for linear and raid0. I'm not sure I would trust any other > configuration. > > Are you seriously using raid1 with non-persistent superblocks? Yes, and this works fine in 2.4, as well. We opted for non-persistent superblocks in order to support creation of raid1 mirrors over partitions that already had filesystems or other data present (and yes, we calculate the size of the new md device to make sure the existing data will fit). > How do you ensure reliable re-assembly after a device failure followed by > shutdown? There is a user-level clustering framework that sets up, monitors, and takes down the mirror. Disk failures and other events are handled by this framework. -- Paul