Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1761468AbXFQTyX (ORCPT ); Sun, 17 Jun 2007 15:54:23 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1760486AbXFQTyO (ORCPT ); Sun, 17 Jun 2007 15:54:14 -0400 Received: from twinlark.arctic.org ([207.29.250.54]:52935 "EHLO twinlark.arctic.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1759510AbXFQTyN (ORCPT ); Sun, 17 Jun 2007 15:54:13 -0400 Date: Sun, 17 Jun 2007 12:54:12 -0700 (PDT) From: dean gaudet To: Wakko Warner cc: Neil Brown , david@lang.hm, linux-kernel@vger.kernel.org, linux-raid@vger.kernel.org Subject: Re: limits on raid In-Reply-To: <20070617193025.GA8770@animx.eu.org> Message-ID: References: <18034.479.256870.600360@notabene.brown> <18034.3676.477575.490448@notabene.brown> <20070616020320.GB2002@animx.eu.org> <18035.23867.576212.859440@notabene.brown> <20070616140857.GA4206@animx.eu.org> <20070617132809.GB7806@animx.eu.org> <20070617193025.GA8770@animx.eu.org> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2216 Lines: 53 On Sun, 17 Jun 2007, Wakko Warner wrote: > What benefit would I gain by using an external journel and how big would it > need to be? i don't know how big the journal needs to be... i'm limited by xfs' maximum journal size of 128MiB. i don't have much benchmark data -- but here are some rough notes i took when i was evaluating a umem NVRAM card. since the pata disks in the raid1 have write caching enabled it's somewhat of an unfair comparison, but the important info is the 88 seconds for internal journal vs. 81 seconds for external journal. -dean time sh -c 'tar xf /var/tmp/linux-2.6.20.tar; sync' xfs journal raid5 bitmap times internal none 0.18s user 2.14s system 2% cpu 1:27.95 total internal internal 0.16s user 2.16s system 1% cpu 2:01.12 total raid1 none 0.07s user 2.02s system 2% cpu 1:20.62 total raid1 internal 0.14s user 2.01s system 1% cpu 1:55.18 total raid1 raid1 0.14s user 2.03s system 2% cpu 1:20.61 total umem none 0.13s user 2.07s system 2% cpu 1:20.77 total umem internal 0.15s user 2.16s system 2% cpu 1:51.28 total umem umem 0.12s user 2.13s system 2% cpu 1:20.50 total raid5: - 4x seagate 7200.10 400GB on marvell MV88SX6081 - mdadm --create --level=5 --raid-devices=4 /dev/md4 /dev/sd[abcd]1 raid1: - 2x maxtor 6Y200P0 on 3ware 7504 - two 128MiB partitions starting at cyl 1 - mdadm --create --level=1 --raid-disks=2 --auto=yes --assume-clean /dev/md1 /dev/sd[fg]1 - mdadm --create --level=1 --raid-disks=2 --auto=yes --assume-clean /dev/md2 /dev/sd[fg]2 - md1 is used for external xfs journal - md2 has an ext3 filesystem for the external md4 bitmap xfs: - mkfs.xfs issued before each run using the defaults (aside from -l logdev=/dev/md1) - mount -o noatime,nodiratime[,logdev=/dev/md1] umem: - 512MiB Micro Memory MM-5415CN - 2 partitions similar to the raid1 setup - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/