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Saturday I added a new drive to my mdadm array, and the reshape process is taking a long time. Unfortunately there's a nasty storm coming, and I'm likely going to lose power, which will probably do bad things to my mdadm grow operation.

Current Status

# cat /proc/mdstat
Personalities : [linear] [multipath] [raid0] [raid1] [raid6] [raid5] [raid4] [raid10]
md0 : active raid5 sdh1[6] sdc1[0] sdg1[5] sdf1[3] sde1[2] sdd1[1]
    11720534016 blocks super 1.2 level 5, 512k chunk, algorithm 2 [6/6] [UUUUUU]
    [=====>...............]  reshape = 25.9% (759125024/2930133504) finish=4091.0min speed=8844K/sec

mdadm --detail /dev/md0

 mdadm --detail /dev/md0
/dev/md0:
        Version : 1.2
  Creation Time : Sat Mar 23 07:41:24 2013
     Raid Level : raid5
     Array Size : 11720534016 (11177.57 GiB 12001.83 GB)
  Used Dev Size : 2930133504 (2794.39 GiB 3000.46 GB)
   Raid Devices : 6
  Total Devices : 6
    Persistence : Superblock is persistent

    Update Time : Tue May 13 11:34:08 2014
          State : clean, reshaping
 Active Devices : 6
Working Devices : 6
 Failed Devices : 0
  Spare Devices : 0

         Layout : left-symmetric
     Chunk Size : 512K

 Reshape Status : 26% complete
  Delta Devices : 1, (5->6)

           Name : foxery:0  (local to host foxery)
           UUID : afbbf397:afc6ac78:6e7d376b:eedc2dd0
         Events : 9641

    Number   Major   Minor   RaidDevice State
       0       8       33        0      active sync   /dev/sdc1
       1       8       49        1      active sync   /dev/sdd1
       2       8       65        2      active sync   /dev/sde1
       3       8       81        3      active sync   /dev/sdf1
       5       8       97        4      active sync   /dev/sdg1
       6       8      113        5      active sync   /dev/sdh1
  1. Is it possible to stop/pause the mdadm grow process?
  2. Can I stop/abort the reshape process, and run with bitmaps?

I used this doc to improve speeds but it didn't do all that much since most of the speed would come from enabling bitmapping, which isn't doable on the fly, afaik.

1

You can try to suspend it by issuing:-

echo "idle" >  /sys/block/md0/md/sync_action

As root.

Then immediately shut it down, so nothing else kicks in a reshape.

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1
echo frozen > /sys/block/md0/md/sync_action

Idle will move the reshare to the next block , ex if it was md0 , it will reshape md1. If you try it again , it will back reshape md0.

So frozen will pause them with indication: resync=PENDING

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