From mboxrd@z Thu Jan 1 00:00:00 1970 From: Marc MERLIN Subject: Intent Bitmap size and performance Date: Sat, 1 Feb 2014 16:39:15 -0800 Message-ID: <20140202003915.GB25441@merlins.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline Sender: linux-raid-owner@vger.kernel.org To: linux-raid@vger.kernel.org List-Id: linux-raid.ids I was reading http://blog.liw.fi/posts/write-intent-bitmaps/ which warns that intent bitmaps kill performance if they are too small The mdadm man page does tell me how I can set the intent bitmap size, but I can't tell what size I have or what is applied by default if you don't have the size option and create the intent bitmap with --grow First, I did: mdadm --grow --bitmap=internal /dev/md7 Then, I have: gargamel:/mnt/btrfs_pool1# mdadm --detail /dev/md7 /dev/md7: Version : 1.2 Creation Time : Thu Mar 25 20:15:00 2010 Raid Level : raid5 Array Size : 7814045696 (7452.05 GiB 8001.58 GB) Used Dev Size : 1953511424 (1863.01 GiB 2000.40 GB) Raid Devices : 5 Total Devices : 5 Persistence : Superblock is persistent Intent Bitmap : Internal Update Time : Sat Feb 1 16:08:56 2014 State : active Active Devices : 5 Working Devices : 5 Failed Devices : 0 Spare Devices : 0 Layout : left-symmetric Chunk Size : 512K Name : gargamel.svh.merlins.org:7 (local to host gargamel.svh.merlins.org) UUID : 5884576b:0e402a5d:8629093c:ec020760 Events : 38030 Number Major Minor RaidDevice State 6 8 81 0 active sync /dev/sdf1 1 8 49 1 active sync /dev/sdd1 2 8 65 2 active sync /dev/sde1 3 8 1 3 active sync /dev/sda1 7 8 17 4 active sync /dev/sdb1 How can I tell I got the size for my array size? Thanks, Marc -- "A mouse is a device used to point at the xterm you want to type in" - A.S.R. Microsoft is to operating systems .... .... what McDonalds is to gourmet cooking Home page: http://marc.merlins.org/ | PGP 1024R/763BE901