From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from dkim2.fusionio.com ([66.114.96.54]:33948 "EHLO dkim2.fusionio.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755340Ab3HLNsp (ORCPT ); Mon, 12 Aug 2013 09:48:45 -0400 Received: from mx2.fusionio.com (unknown [10.101.1.160]) by dkim2.fusionio.com (Postfix) with ESMTP id E2A119A0406 for ; Mon, 12 Aug 2013 07:48:44 -0600 (MDT) Date: Mon, 12 Aug 2013 09:48:40 -0400 From: Josef Bacik To: Kai Krakow CC: Subject: Re: Why does btrfs benchmark so badly in this case? Message-ID: <20130812134840.GA2150@localhost.localdomain> References: <20130808194015.GH16712@localhost.localdomain> <20130808203855.GI16712@localhost.localdomain> <8u3gda-evs.ln1@hurikhan77.spdns.de> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" In-Reply-To: <8u3gda-evs.ln1@hurikhan77.spdns.de> Sender: linux-btrfs-owner@vger.kernel.org List-ID: On Fri, Aug 09, 2013 at 11:35:33PM +0200, Kai Krakow wrote: > Josef Bacik schrieb: > > >> So I guess the reason that ZFS does well with that workload is that > >> ZFS is using smaller blocks, maybe just 512B ? > > > > Yeah I'm not sure what ZFS does, but if you are writing over a block and > > the size/offset isn't aligned then you'd see similar issues with ZFS since > > it would > > have to read+modify+write. It is likely that ZFS just is using a smaller > > blocksize. > > From what I remember, ZFS uses dynamic block sizes. However, block size can > be forced and thus tuned for workloads that require it: > > http://www.joyent.com/blog/bruning-questions-zfs-record-size > > Maybe that's the reason... > > It would be interesting to see how the benchmarks performed with forced > block size. > When I did bs=4k in the fio job to force it to use 4k blocksizes we performed the same as ext4 and xfs. Thanks, Josef