From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from magic.merlins.org ([209.81.13.136]:48756 "EHLO mail1.merlins.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753940AbcBWSac (ORCPT ); Tue, 23 Feb 2016 13:30:32 -0500 Date: Tue, 23 Feb 2016 10:30:21 -0800 From: Marc MERLIN To: Lionel Bouton Cc: Duncan <1i5t5.duncan@cox.net>, Nazar Mokrynskyi , Alexander Fougner , linux-btrfs@vger.kernel.org Message-ID: <20160223183021.GM22487@merlins.org> References: <04df0eaf-9dc8-b9fa-05cb-020507940bed@mokrynskyi.com> <20160223172635.GI22487@merlins.org> <20160223173444.GJ22487@merlins.org> <56CC9E90.30509@bouton.name> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii In-Reply-To: <56CC9E90.30509@bouton.name> Subject: Re: Major HDD performance degradation on btrfs receive Sender: linux-btrfs-owner@vger.kernel.org List-ID: On Tue, Feb 23, 2016 at 07:01:52PM +0100, Lionel Bouton wrote: > Why don't you use autodefrag ? If you have writable snapshots and do > write to them heavily it would not be a good idea (depending on how > BTRFS handles this in most cases you would probably either break the > reflinks or fragment a snapshot to defragment another) but if you only > have read-only snapshots it may work for you (it does for me). It's not a stupid question, I had issues with autodefrag in the past, and turned it off, but it's been a good 2 years, so maybe it works well enough now. > The only BTRFS filesystems where I disabled autodefrag where Ceph OSDs > with heavy in-place updates. Another option would have been to mark > files NoCoW but I didn't want to abandon BTRFS checksumming. Right. I don't have to worry about COW for virtualbox images there, and the snapshots are read only (well, my script makes read-write snapshots too, but I almost never use them. Hopefully their presence isn't a problem, right?) Thanks for the suggestion. Marc -- "A mouse is a device used to point at the xterm you want to type in" - A.S.R. Microsoft is to operating systems .... .... what McDonalds is to gourmet cooking Home page: http://marc.merlins.org/ | PGP 1024R/763BE901