From mboxrd@z Thu Jan 1 00:00:00 1970 From: Brad Campbell Subject: Raid-6 Rebuild question Date: Sun, 13 Nov 2005 13:05:34 +0400 Message-ID: <437701DE.7060400@wasp.net.au> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Return-path: Sender: linux-raid-owner@vger.kernel.org To: RAID Linux List-Id: linux-raid.ids G'day all, Here is an interesting question( well I think so in any case ). I just replaced a failed disk in my 15 drive Raid-6. Simply mdadm --add /dev/md0 /dev/sdl Why, when there is no other activity on the array at all, is it writing to every disk during the recovery? I would have assumed it just read from the others and write to sdl. This is an iostat -k 5 on that machine while rebuilding avg-cpu: %user %nice %sys %iowait %idle 0.00 0.00 100.00 0.00 0.00 Device: tps kB_read/s kB_wrtn/s kB_read kB_wrtn sda 121.08 14187.95 925.30 23552 1536 sdb 127.71 14187.95 1002.41 23552 1664 sdc 125.30 14187.95 1002.41 23552 1664 sdd 122.29 14187.95 1002.41 23552 1664 sde 125.30 14187.95 1002.41 23552 1664 sdf 127.71 14187.95 1002.41 23552 1664 sdg 125.90 14187.95 925.30 23552 1536 sdh 125.30 14187.95 925.30 23552 1536 sdi 134.34 14187.95 925.30 23552 1536 sdj 137.95 14187.95 925.30 23552 1536 sdk 140.36 14187.95 1850.60 23552 3072 sdl 79.52 0.00 14265.06 0 23680 sdm 133.13 14187.95 925.30 23552 1536 sdn 134.34 14187.95 925.30 23552 1536 sdo 133.73 14187.95 925.30 23552 1536 md0 0.00 0.00 0.00 0 0 storage1:/home/brad# cat /proc/mdstat Personalities : [raid6] md0 : active raid6 sdl[15] sdg[6] sda[0] sdo[14] sdn[13] sdm[12] sdk[10] sdj[9] sdi[8] sdh[7] sdf[5] sde[4] sdd[3] sdc[2] sdb[1] 3186525056 blocks level 6, 128k chunk, algorithm 2 [15/14] [UUUUUUUUUUU_UUU] [>....................] recovery = 1.8% (4518144/245117312) finish=838.3min speed=4782K/sec unused devices: Regards, Brad -- "Human beings, who are almost unique in having the ability to learn from the experience of others, are also remarkable for their apparent disinclination to do so." -- Douglas Adams