$ sudo mdadm --detail /dev/md0
/dev/md0:
Version : 1.2
Creation Time : Sat Nov 12 17:07:34 2016
Raid Level : raid10
Array Size : 3906766848 (3725.78 GiB 4000.53 GB)
Used Dev Size : 1953383424 (1862.89 GiB 2000.26 GB)
Raid Devices : 4
Total Devices : 4
Persistence : Superblock is persistent
Intent Bitmap : Internal
Update Time : Sat Nov 12 17:37:03 2016
State : clean, resyncing
Active Devices : 4
Working Devices : 4
Failed Devices : 0
Spare Devices : 0
Layout : near=2
Chunk Size : 512K
Resync Status : 8% complete
Name : aucklandserver:0 (local to host aucklandserver)
UUID : 39f6ba98:f43d7886:e23e8af7:5330965d
Events : 337
Number Major Minor RaidDevice State
0 8 0 0 active sync set-A /dev/sda
1 8 16 1 active sync set-B /dev/sdb
2 8 32 2 active sync set-A /dev/sdc
3 8 48 3 active sync set-B /dev/sdd