From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from plane.gmane.org ([80.91.229.3]:38926 "EHLO plane.gmane.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751078AbaI0Cgd (ORCPT ); Fri, 26 Sep 2014 22:36:33 -0400 Received: from list by plane.gmane.org with local (Exim 4.69) (envelope-from ) id 1XXhs7-0000E5-96 for linux-btrfs@vger.kernel.org; Sat, 27 Sep 2014 04:36:31 +0200 Received: from ip68-231-22-224.ph.ph.cox.net ([68.231.22.224]) by main.gmane.org with esmtp (Gmexim 0.1 (Debian)) id 1AlnuQ-0007hv-00 for ; Sat, 27 Sep 2014 04:36:31 +0200 Received: from 1i5t5.duncan by ip68-231-22-224.ph.ph.cox.net with local (Gmexim 0.1 (Debian)) id 1AlnuQ-0007hv-00 for ; Sat, 27 Sep 2014 04:36:31 +0200 To: linux-btrfs@vger.kernel.org From: Duncan <1i5t5.duncan@cox.net> Subject: Re: 3.16 Managed to ENOSPC with <80% used Date: Sat, 27 Sep 2014 02:36:12 +0000 (UTC) Message-ID: References: Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Sender: linux-btrfs-owner@vger.kernel.org List-ID: Rich Freeman posted on Fri, 26 Sep 2014 10:18:37 -0400 as excerpted: > On Thu, Sep 25, 2014 at 5:21 PM, Holger Hoffstätte > wrote: >> That's why I mentioned adding a second device - that will immediately >> allow cleanup with headroom. An additional 8GB tmpfs volume can works >> wonders. >> >> > If you add a single 8GB tmpfs to a RAID1 btrfs array, is it safe to > assume that you'll still always have a redundant copy of everything on a > disk somewhere during the recovery? Would only a single tmpfs volume > actually help in this case? I get a bit nervous about doing a cleanup > that involves moving metadata to tmpfs of all places, since some kind of > deadlock/etc could result in unrecoverable data loss. > > Doing the same thing with an actual hard drive would concern me less. That has been my concern too, and why I'd be leery about using a loopback on tmpfs, even for the few minutes (more like seconds since I'm on SSD and we /are/ talking memory-backed tmpfs) it'd take to free a minimal number of chunks (say usage=2% or 5% or whatever, the smallest number that actually frees anything). With SSD and with backups I'd probably do it, but it's not something I could recommend, and I'm not sure I'd do it on slower spinning rust, just because the time is longer. I'd probably use a thumb drive or the like, instead, and would certainly recommend that to others, altho if they're comfortable with it and want to risk it, a loopback file on tmpfs should work fine, provided the power doesn't go out in the middle or something. -- Duncan - List replies preferred. No HTML msgs. "Every nonfree program has a lord, a master -- and if you use the program, he is your master." Richard Stallman