Today I started the migration of my Raid 5 to Raid 6 by adding a new disk (going from 7 to 8 disks, all 3TB). Now the reshape is in progress: Personalities : [raid6] [raid5] [raid4] md0 : active raid6 sdi[9] sdh[8] sdf[7] sdc[6] sdd[4] sda[0] sde[5] sdb[1]      17581590528 blocks super 1.2 level 6, 512k chunk, algorithm 18 [8/7] [UUUUUUU_]      [>....................]  reshape =  2.3% (69393920/2930265088) finish=6697.7min speed=7118K/secunused devices: <none>but it is slow as hell. It will be almost 5 days before completion. I was using to reshape the array in about 1 day, but here it is horrible. The speed is very low. The backup file is on a SSD. I did change the stripe size and the min and max speed limits, and it did not change a thing. Is there any way I can speed up the process to reasonable amount of time or I have to wait 5 days to finish ?Update: iostat -kx 10avg-cpu:  %user   %nice %system %iowait  %steal   %idle           0.05    0.00    1.68   22.07    0.00   76.20Device:         rrqm/s   wrqm/s     r/s     w/s    rkB/s    wkB/s avgrq-sz avgqu-sz   await r_await w_await  svctm  %utilsda            1675.90  1723.00   27.60   23.90 13875.20  6970.00   809.52     0.55   10.79    8.59   13.33   7.97  41.02sdb            1675.90  1723.10   27.20   23.80 13670.40  6970.00   809.43     0.55   10.80    8.96   12.90   8.12  41.43sdc            1675.90  1723.60   27.50   23.30 13824.00  6970.00   818.66     0.65   12.85   10.48   15.65   9.83  49.94sdd            1675.90  1723.10   27.60   23.80 13875.20  6970.00   811.10     0.55   10.80    8.93   12.98   8.16  41.95sde            1675.90  1723.10   27.20   23.80 13670.40  6970.00   809.43     0.60   11.79    9.17   14.79   9.19  46.87sdf            1675.90  1723.80   27.70   23.10 13926.40  6970.00   822.69     0.72   14.28   11.65   17.43  10.12  51.40sdg               0.00     4.10    0.00   93.20     0.00 39391.20   845.30     6.07   65.14    0.00   65.14   2.71  25.29dm-0              0.00     0.00    0.00    4.30     0.00    18.40     8.56     0.00    0.07    0.00    0.07   0.02   0.01dm-1              0.00     0.00    0.00   89.60     0.00 39372.80   878.86     6.07   67.78    0.00   67.78   2.82  25.28md0               0.00     0.00    0.00    0.00     0.00     0.00     0.00     0.00    0.00    0.00    0.00   0.00   0.00sdh            1583.50  1631.70  216.50  115.90 13824.00  6970.00   125.11     1.56    4.73    5.36    3.55   0.43  14.41sdi               0.00  1631.70    0.00  115.90     0.00  6970.00   120.28     0.21    1.77    0.00    1.77   0.28   3.25dm-2              0.00     0.00    0.00    0.00     0.00     0.00     0.00     0.00    0.00    0.00    0.00   0.00   0.00dm-3              0.00     0.00    0.00    0.00     0.00     0.00     0.00     0.00    0.00    0.00    0.00   0.00   0.00dm-4              0.00     0.00    0.00    0.00     0.00     0.00     0.00     0.00    0.00    0.00    0.00   0.00   0.00sdi is the disk I last added. sdg is the SSD. The dmX are the partitions on LVM. 
How to speed up migration from Raid 5 to Raid 6 with mdadm?
mdadm
It seems to me that it is related to the mdadm migration from raid 5 to raid 6. I have just added a new disk to the array and the grow speed is totally reasonable (40000K/s) for my hardware. 