From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from plane.gmane.org ([80.91.229.3]:54965 "EHLO plane.gmane.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751222AbcDDGJx (ORCPT ); Mon, 4 Apr 2016 02:09:53 -0400 Received: from list by plane.gmane.org with local (Exim 4.69) (envelope-from ) id 1amxhs-0007dR-Nk for linux-btrfs@vger.kernel.org; Mon, 04 Apr 2016 08:09:48 +0200 Received: from ip98-167-165-199.ph.ph.cox.net ([98.167.165.199]) by main.gmane.org with esmtp (Gmexim 0.1 (Debian)) id 1AlnuQ-0007hv-00 for ; Mon, 04 Apr 2016 08:09:48 +0200 Received: from 1i5t5.duncan by ip98-167-165-199.ph.ph.cox.net with local (Gmexim 0.1 (Debian)) id 1AlnuQ-0007hv-00 for ; Mon, 04 Apr 2016 08:09:48 +0200 To: linux-btrfs@vger.kernel.org From: Duncan <1i5t5.duncan@cox.net> Subject: Re: [PATCH 00/13 v3] Introduce device state 'failed', Hot spare and Auto replace Date: Mon, 4 Apr 2016 06:09:41 +0000 (UTC) Message-ID: References: <1459560651-14809-1-git-send-email-anand.jain@oracle.com> <20160404020043.47ad35bf@jupiter.sol.kaishome.de> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Sender: linux-btrfs-owner@vger.kernel.org List-ID: Duncan posted on Mon, 04 Apr 2016 04:45:16 +0000 as excerpted: > Kai Krakow posted on Mon, 04 Apr 2016 02:00:43 +0200 as excerpted: > >> Does this also implement "copy-back" - thus, it returns the hot-spare >> device to global hot-spares when the failed device has been replaced? > > I don't believe it does that in this initial implementation, anyway. > > There's a number of issues with the initial implementation, including > the fact that the hot-spare is global only and can't be specifically > assigned to a filesystem or set of filesystems, which means, if you have > multiple filesystems using different sized devices, the hot-spares must > be sized to match the largest device they could replace, Obviously the sizes issue is problematic for the hot-spare-return situation as well, since it would then be possible for an appropriately large replacement device to replace a much smaller device on some filesystem, which would then put the much smaller device into rotation as a hot-spare where it could end up picked to replace a far larger device. As there's currently no intelligence as to device sizes, etc, it just picks the next device in the hot-spares list and tries to use it, oops! So hot-spare-return really will need to wait until per-filesystem hot- spares and/or some sizing intelligence is added. -- Duncan - List replies preferred. No HTML msgs. "Every nonfree program has a lord, a master -- and if you use the program, he is your master." Richard Stallman