From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mx0a-00082601.pphosted.com ([67.231.145.42]:14511 "EHLO mx0a-00082601.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751396AbaLSVQF (ORCPT ); Fri, 19 Dec 2014 16:16:05 -0500 Message-ID: <5494955C.3020603@fb.com> Date: Fri, 19 Dec 2014 16:15:08 -0500 From: Josef Bacik MIME-Version: 1.0 To: Daniele Testa , Phillip Susi CC: Subject: Re: btrfs is using 25% more disk than it should References: <54947432.5010107@ubuntu.com> In-Reply-To: Content-Type: text/plain; charset="utf-8"; format=flowed Sender: linux-btrfs-owner@vger.kernel.org List-ID: On 12/19/2014 02:59 PM, Daniele Testa wrote: > No, I don't have any snapshots or subvolumes. Only that single file. > > The file has both checksums and datacow on it. I will do "chattr +C" > on the parent dir and re-create the file to make sure all files are > marked as "nodatacow". > > Should I also turn off checksums with the mount-flags if this > filesystem only contain big VM-files? Or is it not needed if I put +C > on the parent dir? Please God don't turn off of checksums. Checksums are tracked in metadata anyway, they won't show up in the data accounting. Our csums are 8 bytes per block, so basic math says you are going to max out at 604 megabytes for that big of a file. Please people try to only take advice from people who know what they are talking about. So unless it's from somebody who has commits in btrfs/btrfs-progs take their feedback with a grain of salt. Thanks, Josef