From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-it0-f51.google.com ([209.85.214.51]:45289 "EHLO mail-it0-f51.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751443AbdLDMSO (ORCPT ); Mon, 4 Dec 2017 07:18:14 -0500 Received: by mail-it0-f51.google.com with SMTP id z6so12212442iti.4 for ; Mon, 04 Dec 2017 04:18:14 -0800 (PST) Subject: Re: btrfs-transacti hammering the system To: Matt McKinnon , linux-btrfs@vger.kernel.org References: <9703c200-28af-f26d-b3b2-6982fb289ac8@mendix.com> <1d11e03c-7d02-3f66-8b97-4c1b857566fa@techsquare.com> <5ecddad2-bb6a-2991-c8d0-be97a4541b0d@mendix.com> <113cba02-2557-d1e8-193f-fab4437f1199@techsquare.com> From: "Austin S. Hemmelgarn" Message-ID: <96e81cad-1024-aa9e-c3fe-d884a710b130@gmail.com> Date: Mon, 4 Dec 2017 07:18:11 -0500 MIME-Version: 1.0 In-Reply-To: <113cba02-2557-d1e8-193f-fab4437f1199@techsquare.com> Content-Type: text/plain; charset=utf-8; format=flowed Sender: linux-btrfs-owner@vger.kernel.org List-ID: On 2017-12-01 16:50, Matt McKinnon wrote: > Well, it's at zero now... > > # btrfs fi df /export/ > Data, single: total=30.45TiB, used=30.25TiB > System, DUP: total=32.00MiB, used=3.62MiB > Metadata, DUP: total=66.50GiB, used=65.16GiB > GlobalReserve, single: total=512.00MiB, used=0.00B GlobalReserve seems to be used temporarily for certain cases of metadata COW regardless of how full the FS actually is, I'm betting that it just so happened that such a case was in progress when you got the info previously. If you aren't seeing it regularly used, it's (probably) not an issue. Duncan is correct though when dealing with long-term usage. If you see GlobalReserve usage that persists for an extended period of time, something is almost certainly wrong, especially if the FS isn't close to being full. > > > On 01/12/17 16:47, Duncan wrote: >> Hans van Kranenburg posted on Fri, 01 Dec 2017 18:06:23 +0100 as >> excerpted: >> >>> On 12/01/2017 05:31 PM, Matt McKinnon wrote: >>>> Sorry, I missed your in-line reply: >>>> >>>> >>>>> 2) How big is this filesystem? What does your `btrfs fi df >>>>> /mountpoint` say? >>>>> >>>> >>>> # btrfs fi df /export/ >>>> Data, single: total=30.45TiB, used=30.25TiB >>>> System, DUP: total=32.00MiB, used=3.62MiB >>>> Metadata, DUP: total=66.50GiB, used=65.08GiB >>>> GlobalReserve, single: total=512.00MiB, used=53.69MiB >>> >>> Multi-TiB filesystem, check. total/used ratio looks healthy. >> >> Not so healthy, from here.  Data/metadata are healthy, yes, >> but... >> >> Any usage at all of global reserve is a red flag indicating that >> something in the filesystem thinks, or thought when it resorted >> to global reserve, that space is running out. >> >> Global reserve usage doesn't really hint what the problem is, >> but it's definitely a red flag that there /is/ a problem, and >> it's easily overlooked, as it apparently was here. >> >> It's likely indication of a bug, possibly one of the ones fixed >> right around 4.12/4.13.  I'll let the devs and better experts take >> it from there, but I'd certainly be worried until global reserve >> drops to zero usage. >>