From mboxrd@z Thu Jan 1 00:00:00 1970 From: Phil Turmel Subject: Re: Linux raid wiki Date: Fri, 23 Sep 2016 23:38:12 -0400 Message-ID: References: <57E469E0.4020005@youngman.org.uk> <002a01d215c0$e3f20980$abd61c80$@wnsdev.com> <57E577BE.8080101@youngman.org.uk> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <57E577BE.8080101@youngman.org.uk> Sender: linux-raid-owner@vger.kernel.org To: Wols Lists , WNSDEV , linux-raid@vger.kernel.org List-Id: linux-raid.ids On 09/23/2016 02:43 PM, Wols Lists wrote: > Thanks. > > My understanding of role numbers is that they are the order of the disks > in which stripes are written, so role 0 has the first stripe, role 1 the > second, etc etc. Yes, this is correct. But the numbers in brackets in mdstat aren't the role number, but the slot number in the superblock member list. Which only matches role number for the active devices at first creation. Spares occupy additional slots, and keep their slot number for their life in the array, including after assuming an active role. > This is *normally* irrelevant, but should the array ever get trashed, > the disks need to be listed *in* *that* *order* in a new --create statement. You must use the "this device" role numbers in an mdadm -E report to be sure, or use lsdrv. mdstat is only useful for human review of array status. Phil