Is it possible to pause/abort mdadm reshape?

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.

2 Answers

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

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.