From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail.virtall.com ([178.63.195.102]:51263 "EHLO mail.virtall.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752167Ab3GVFWP (ORCPT ); Mon, 22 Jul 2013 01:22:15 -0400 To: linux-btrfs@vger.kernel.org, 1i5t5.duncan@cox.net, linuxhippy@gmail.com Subject: Re: abysmal rm =?UTF-8?Q?performance=3F?= MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Date: Mon, 22 Jul 2013 12:22:11 +0700 From: Tomasz Chmielewski Message-ID: <827cf884b1a6e12db95beea6912d946b@admin.virtall.com> Sender: linux-btrfs-owner@vger.kernel.org List-ID: > You /really/ need to read up on the btrfs wiki. > > The short answer is yes, btrfs does a LOT more metadata processing > due to the checksumming it does by default. According to the wiki, checksumming has barely any influence, so I guess the above advice is not really helpful? https://btrfs.wiki.kernel.org/index.php/Mount_options nodatasum (...) On most modern CPUs this option does not result in any reasonable performance improvement. > Then there's the whole problem that you didn't provide nearly enough > information about your test to tell what it was actually comparing. > What sort of raid1, btrfs/md/dm/hardware/what, and if btrfs raid1, was > that for both data and metadata or just one of the two and what was > the other one if they weren't both raid1? And if you were testing > btrfs raid1, what did you do with the ext4 test to try to make it > comparable since ext4 doesn't have a native raid1 mode, or was it on > a single device? ext4: using md RAID btrfs: Data, RAID1: total=1.73TB, used=1.36TB System, RAID1: total=32.00MB, used=264.00KB System: total=4.00MB, used=0.00 Metadata, RAID1: total=79.00GB, used=70.23GB Quite high metadata usage here. The filesystems on ext4 and btrfs are copies; there are >30 milion inodes on ext4; most of the files have multiple hardlinks. So paraphrasing my question: is there anything to improve "rm" performance with btrfs? "nodatacow" might help a bit, but then, it disabled the compression, which is a major drawback. -- Tomasz Chmielewski http://wpkg.org