From: Rogier Wolff Subject: Re: Uneven load on my raid disks. Date: Thu, 30 Dec 2010 11:32:01 +0100 Message-ID: <20101230103200.GH2986@bitwizard.nl> References: <20101228090749.GB1351@bitwizard.nl> <4D1B646C.8030100@uni-konstanz.de> <20101229221715.GK10149@thunk.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Kay Diederichs , Rogier Wolff , linux-ext4@vger.kernel.org To: Ted Ts'o Return-path: Received: from dtp.xs4all.nl ([80.101.171.8]:65309 "HELO abra2.bitwizard.nl" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with SMTP id S1752664Ab0L3KcD (ORCPT ); Thu, 30 Dec 2010 05:32:03 -0500 Content-Disposition: inline In-Reply-To: <20101229221715.GK10149@thunk.org> Sender: linux-ext4-owner@vger.kernel.org List-ID: On Wed, Dec 29, 2010 at 05:17:15PM -0500, Ted Ts'o wrote: > On Wed, Dec 29, 2010 at 05:40:12PM +0100, Kay Diederichs wrote: > > >says: dumpe2fs -h /dev/md0 | grep RAID > > > > % tune2fs -l /dev/md0 > > > > ... > > RAID stride: 128 > > RAID stripe width: 768 > > ... > > > > runs much faster than dumpe2fs. > > The command can also adjust the values. > > Actually, "tune2fs -l" and "dumpe2fs -h" both run in about the same > amount of time. dumpe2fs without the -h option runs slower than > tune2fs -l, true. But that's because it reads and prints out > information regarding the block and inode allocation bitmaps. And the annoying thing is that it apparently uses a library function that only returns after reading all that data. So while it could print the superblock info and the first few block groups, I'm left waiting. My remove-of-200-million-files has completed. It took a week. 200000000/7/24/3600 = 330.7 . So it deleted around 330 files per second. With one IO operation per delete, the four disks operating at close to 75 IOs per second have performed reasonable. And at an average of 1 IO per remove, also the filesystem has performed reasonable. It seems I forgot the -E stride= option on mkfs. The manual of tune2fs hints that this can be tuned after the fact with tune2fs. I seriously doubt it. Correct? TUNE2FS(8) ... -E extended-options Set extended options for the filesystem. Extended options are comma separated, and may take an argument using the equals ('=') sign. The following extended options are supported: stride=stride-size ... stripe_width=stripe-width Roger. -- ** R.E.Wolff@BitWizard.nl ** http://www.BitWizard.nl/ ** +31-15-2600998 ** ** Delftechpark 26 2628 XH Delft, The Netherlands. KVK: 27239233 ** *-- BitWizard writes Linux device drivers for any device you may have! --* Q: It doesn't work. A: Look buddy, doesn't work is an ambiguous statement. Does it sit on the couch all day? Is it unemployed? Please be specific! Define 'it' and what it isn't doing. --------- Adapted from lxrbot FAQ