From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from gourmet.spamgourmet.com ([216.75.62.102]:57894 "EHLO gourmet8.spamgourmet.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1759222AbbKST05 (ORCPT ); Thu, 19 Nov 2015 14:26:57 -0500 Received: from spamgourmet by gourmet7.spamgourmet.com with local (Exim 4.80) (envelope-from ) id 1ZzUrA-0005sF-J1 for linux-btrfs@vger.kernel.org; Thu, 19 Nov 2015 19:26:56 +0000 From: linux-btrfs.tebulin@xoxy.net Subject: Re: Kernel 3.19 and still "disk full" even though 'btrfs fi df" reports enough room left? References: <564CC90F.3060703@gmail.com> <20151118190857.GY24333@carfax.org.uk> <564E085C.3060208@gmail.com> <20151119182850.GE24333@carfax.org.uk> <564E18B9.2020509@gmail.com> <20151119185645.GF24333@carfax.org.uk> Message-ID: <564E227C.9000909@gmail.com> Date: Thu, 19 Nov 2015 20:26:52 +0100 MIME-Version: 1.0 To: linux-btrfs@vger.kernel.org In-Reply-To: <20151119185645.GF24333@carfax.org.uk> Content-Type: text/plain; charset=windows-1252 Sender: linux-btrfs-owner@vger.kernel.org List-ID: This explanation helped a lot. Got it now! Thank you! > You start with a load of unused space -- that's the "total" for > each device in btrfs fi show. That space is allocated to specific > usages as the FS needs it. The allocated space is the "used" in btrfs > fi show for each device. > > Then we switch to looking at btrfs fi df. The "total" values are > the amount of the *allocated* space given to each type of storage. > Within those, actual stuff is stored (like your files), which is the > "used" value for each kind of storage. > > If you've ever played SimCity, the allocation process is like > zoning -- you say what kind of thing can go on the space, but it's not > actually used until something gets built on it. > > The problem you hit is when everything has been allocated, and > there's a need for more metadata space (usually), and there's lots of > unused data space. The balance operation moves some things around so > that some of the unused data allocation can be freed up, giving the FS > the ability to allocate more metadata space.