From mboxrd@z Thu Jan 1 00:00:00 1970 From: Josh Durgin Subject: Re: Is using the 'discard' mount option safe on an rbd? Date: Thu, 06 Sep 2012 15:14:48 -0700 Message-ID: <50492058.2030608@inktank.com> References: Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Return-path: Received: from mail-pz0-f46.google.com ([209.85.210.46]:60602 "EHLO mail-pz0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751544Ab2IFWOv (ORCPT ); Thu, 6 Sep 2012 18:14:51 -0400 Received: by dady13 with SMTP id y13so1368642dad.19 for ; Thu, 06 Sep 2012 15:14:51 -0700 (PDT) In-Reply-To: Sender: ceph-devel-owner@vger.kernel.org List-ID: To: Nick Bartos Cc: ceph-devel@vger.kernel.org On 09/06/2012 02:57 PM, Nick Bartos wrote: > Is it safe to use the discard mount option when mounting a xfs > filesystem on an rbd (using the kernel driver)? We're currently using > kernel 3.5.3 and Ceph 0.48.1. The kernel rbd driver doesn't support discard yet (http://tracker.newdream.net/issues/190). > Also, are there any stability issues doing it from a qemu VM? It > looks like support for rbd discard was added in qemu 1.1, but I wasn't > sure how stable it was. There was one bug (http://tracker.newdream.net/issues/2958) whose fix will be in the next release. Note that you need an extra qemu option (http://tracker.newdream.net/issues/2777) for the guest to detect discard support. Josh