From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from relay.sgi.com (relay3.corp.sgi.com [198.149.34.15]) by oss.sgi.com (Postfix) with ESMTP id 95D867F3F for ; Wed, 29 Oct 2014 08:03:14 -0500 (CDT) Received: from cuda.sgi.com (cuda1.sgi.com [192.48.157.11]) by relay3.corp.sgi.com (Postfix) with ESMTP id 42192AC007 for ; Wed, 29 Oct 2014 06:03:14 -0700 (PDT) Received: from sandeen.net (sandeen.net [63.231.237.45]) by cuda.sgi.com with ESMTP id uWHHs1Uc83JAjPQs for ; Wed, 29 Oct 2014 06:03:09 -0700 (PDT) Message-ID: <5450E58B.10106@sandeen.net> Date: Wed, 29 Oct 2014 08:03:07 -0500 From: Eric Sandeen MIME-Version: 1.0 Subject: Re: XFS shrinking planned? References: <544FC202.1000200@shiftmail.org> <544FD4C1.4020004@sandeen.net> <5450B560.6000208@shiftmail.org> In-Reply-To: <5450B560.6000208@shiftmail.org> List-Id: XFS Filesystem from SGI List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: xfs-bounces@oss.sgi.com Sender: xfs-bounces@oss.sgi.com To: Spelic , xfs@oss.sgi.com On 10/29/14 4:37 AM, Spelic wrote: > On 28/10/2014 18:39, Eric Sandeen wrote: >> Not formally planned, there are bits and pieces out there (i.e. the inode >> mover) which are part of what it might take to achieve a shrinker. >> >> Another option, rather than fs shrinking, is to use the dm-thinp target, which >> would allow you to allocate a large-but-sparse block device, create a very >> large filesystem on that, and add or remove storage as needed. >> (At least I think you can remove it...!) >> >> -Eric > > Thanks for your reply Eric > > Interesting technique, but for enforcing a maximum size (smaller than > the very large allocated thin device) I would have to rely on quotas, > which probably decreases performance. "probably" > Then using thinp would mess up > all the disk layout, basically replacing the XFS allocator, which > most likely would decrease performances significantly. "most likely" > And then the > thinp code itself is a medium performance thing and I don't think it > can keep up with XFS performances, so that would presumably be a hard > bottleneck. "presumably" > All this would result in a performance almost certainly > lower than ext4. "almost certainly..." All possibilities, but possibly also worth testing to find out. ;) It's true that today the thinp allocator will impact XFS allocation patterns to some degree. Anyway, shrink has been on the radar for years, it's just never really been a priority. It might happen some day... -Eric > Thanks > S. > _______________________________________________ xfs mailing list xfs@oss.sgi.com http://oss.sgi.com/mailman/listinfo/xfs