From mboxrd@z Thu Jan 1 00:00:00 1970 From: Dave Chinner Subject: Re: Fwd: Fwd: [newstore (again)] how disable double write WAL Date: Tue, 16 Feb 2016 14:35:38 +1100 Message-ID: <20160216033538.GB2005@devil.localdomain> References: <9D046674-EA8B-4CB5-B049-3CF665D4ED64@aevoo.fr> <5661F3A9.8070703@redhat.com> <20151208044640.GL1983@devil.localdomain> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Received: from mx1.redhat.com ([209.132.183.28]:36521 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752759AbcBPDfo (ORCPT ); Mon, 15 Feb 2016 22:35:44 -0500 Content-Disposition: inline In-Reply-To: Sender: ceph-devel-owner@vger.kernel.org List-ID: To: David Casier Cc: Ric Wheeler , Sage Weil , Ceph Development , Brian Foster , Eric Sandeen On Mon, Feb 15, 2016 at 04:18:28PM +0100, David Casier wrote: > Hi Dave, > 1TB is very wide for SSD. It fills from the bottom, so you don't need 1TB to make it work in a similar manner to the ext4 hack being described. > Exemple with only 10GiB : > https://www.aevoo.fr/2016/02/14/ceph-ext4-optimisation-for-filestore/ It's a nice toy, but it's not something that is going scale reliably for production. That caveat at the end: "With this model, filestore rearrange the tree very frequently : + 40 I/O every 32 objects link/unlink." Indicates how bad the IO patterns will be when modifying the directory structure, and says to me that it's not a useful optimisation at all when you might be creating several thousand files/s on a filesystem. That will end up IO bound, SSD or not. Cheers, Dave. -- Dave Chinner dchinner@redhat.com