From mboxrd@z Thu Jan  1 00:00:00 1970
From: Ted Ts'o <tytso@mit.edu>
Subject: Re: BTRFS: Unbelievably slow with kvm/qemu
Date: Wed, 1 Sep 2010 20:18:59 -0400
Message-ID: <20100902001859.GA4930@thunk.org>
References: <4C7AB645.5090804@wpkg.org>
 <20100830001441.GA838@dhcp231-156.rdu.redhat.com>
 <4C7BD569.9000702@noir.com>
 <AANLkTin-BZvqCChXEmsDfjhVmRmJLaoaudnuFL6EXZQx@mail.gmail.com>
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Cc: Mike Fedyk <mfedyk@mikefedyk.com>, Josef Bacik <josef@redhat.com>,
	Tomasz Chmielewski <mangoo@wpkg.org>,
	linux-kernel@vger.kernel.org, linux-btrfs@vger.kernel.org,
	hch@infradead.org, gg.mariotti@gmail.com,
	"Justin P. Mattock" <justinmattock@gmail.com>, mjt@tls.msk.ru
To: "K. Richard Pixley" <rich@noir.com>
Return-path: <linux-kernel-owner@vger.kernel.org>
In-Reply-To: <4C7D7B14.9020008@noir.com>
List-ID: <linux-btrfs.vger.kernel.org>

On Tue, Aug 31, 2010 at 02:58:44PM -0700, K. Richard Pixley wrote:
>  On 20100831 14:46, Mike Fedyk wrote:
> >There is little reason not to use duplicate metadata.  Only small
> >files (less than 2kb) get stored in the tree, so there should be no
> >worries about images being duplicated without data duplication set at
> >mkfs time.
> My benchmarks show that for my kinds of data, btrfs is somewhat
> slower than ext4, (which is slightly slower than ext3 which is
> somewhat slower than ext2), when using the defaults, (ie, duplicate
> metadata).
> 
> It's a hair faster than ext2, (the fastest of the ext family), when
> using singleton metadata.  And ext2 isn't even crash resistant while
> btrfs has snapshots.

I'm really, really curious.  Can you describe your data and your
workload in detail?  You mentioned "continuous builders"; is this some
kind of tinderbox setup?

						- Ted