From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from smtp89.ord1c.emailsrvr.com ([108.166.43.89]:60959 "EHLO smtp89.ord1c.emailsrvr.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751138AbbFQNNY convert rfc822-to-8bit (ORCPT ); Wed, 17 Jun 2015 09:13:24 -0400 Received: from smtp12.relay.ord1c.emailsrvr.com (localhost.localdomain [127.0.0.1]) by smtp12.relay.ord1c.emailsrvr.com (SMTP Server) with ESMTP id 0860C38028B for ; Wed, 17 Jun 2015 09:13:23 -0400 (EDT) Received: from smtp12.relay.ord1c.emailsrvr.com (localhost.localdomain [127.0.0.1]) by smtp12.relay.ord1c.emailsrvr.com (SMTP Server) with ESMTP id D86BC38029E for ; Wed, 17 Jun 2015 09:13:23 -0400 (EDT) Received: by smtp12.relay.ord1c.emailsrvr.com (Authenticated sender: vincent-AT-up4.tv) with ESMTPSA id BBB0638028B for ; Wed, 17 Jun 2015 09:13:16 -0400 (EDT) Content-Type: text/plain; charset=utf-8 Mime-Version: 1.0 (Mac OS X Mail 8.2 \(2098\)) Subject: Re: RAID10 Balancing Request for Comments and Advices From: Vincent Olivier In-Reply-To: Date: Wed, 17 Jun 2015 09:13:08 -0400 Message-Id: <80BA2964-3B67-430B-99BE-62A348C5DBED@up4.com> References: <1434456557.89597618@apps.rackspace.com> <20150616122545.GI9850@carfax.org.uk> <61CBE6C4-0D06-4F16-B522-4DBB756FBC31@up4.com> To: linux-btrfs@vger.kernel.org Sender: linux-btrfs-owner@vger.kernel.org List-ID: > On Jun 16, 2015, at 8:14 PM, Chris Murphy wrote: > > On Tue, Jun 16, 2015 at 5:58 PM, Duncan <1i5t5.duncan@cox.net> wrote: > >> On a current kernel unlike older ones, btrfs actually automates entirely >> empty chunk reclaim, so this problem doesn't occur anything close to near >> as often as it used to. However, it's still possible to have mostly but >> not entirely empty chunks that btrfs won't automatically reclaim. A >> balance can be used to rewrite and combine these mostly empty chunks, >> reclaiming the space saved. This is what Hugo was recommending. > > Yes, as little as a -dusage=5 (data chunks that are 5% or less full) > can clear the problem and is very fast, seconds. Possibly a bit > longer, many seconds o single digit minutes is -dusage=15. I haven't > done a full balance in forever. Yes, on this 80% full 6x4TB RAID10 -dusage=15 took 2 seconds and relocated "0 out of 3026 chunks”. Out of curiosity, I had to use -dusage=90 to have it relocate only 1 chunk and it took les than 30 seconds. So I put a -dusage=25 in the weekly cron just before the scrub. FYI. Thanks for your help.