I previously had a raid5 with mdadm using four 2TB drives. I've recently disassembled the raid and created a raid10 with six 2TB drives, but mdadm --detail is showing "Used Dev Size" as only 2TB (the original one disk raid5 parity) instead of the expected 6TB (half of the new 12TB).
Q: Is having this field at 2TB instead of 6TB going to be an issue? Even if it might be fine, I still don't like seeing it wrong.
I'm using CentOS 6.3 (2.6.32-279.9.1.el6.i686) with mdadm 3.2.3-9.el6.i686
I zeroed all the superblocks when I disassembled the raid5:
sudo mdadm --zero-superblock /dev/sda1
Created the array with:
sudo mdadm -v --create /dev/md0 --level=raid10 --raid-devices=6 /dev/sd[a-f]1
Current output of mdadm --detail
sudo mdadm --detail /dev/md0
/dev/md0:
Version : 1.2
Creation Time : Thu Sep 27 09:31:33 2012
Raid Level : raid10
Array Size : 5860535808 (5589.04 GiB 6001.19 GB)
Used Dev Size : 1953511936 (1863.01 GiB 2000.40 GB)
Raid Devices : 6
Total Devices : 6
Persistence : Superblock is persistent
Update Time : Fri Sep 28 09:42:55 2012
State : clean
Active Devices : 6
Working Devices : 6
Failed Devices : 0
Spare Devices : 0
Layout : near=2
Chunk Size : 512K
Name : mega-breff:0 (local to host mega-breff)
UUID : 08d9e66b:c1218cd5:6c8f0cb8:fd144d20
Events : 19
Number Major Minor RaidDevice State
0 8 1 0 active sync /dev/sda1
1 8 17 1 active sync /dev/sdb1
2 8 33 2 active sync /dev/sdc1
3 8 49 3 active sync /dev/sdd1
4 8 65 4 active sync /dev/sde1
5 8 81 5 active sync /dev/sdf1
Output of gdisk (each disk has the exact same partition layout):
sudo gdisk -l /dev/sda
GPT fdisk (gdisk) version 0.8.4
Partition table scan:
MBR: protective
BSD: not present
APM: not present
GPT: present
Found valid GPT with protective MBR; using GPT.
Disk /dev/sda: 3907029168 sectors, 1.8 TiB
Logical sector size: 512 bytes
Disk identifier (GUID): 742B7071-DAB2-4C74-9522-FC18D2EE135E
Partition table holds up to 128 entries
First usable sector is 34, last usable sector is 3907029134
Partitions will be aligned on 2048-sector boundaries
Total free space is 2148 sectors (1.0 MiB)
Number Start (sector) End (sector) Size Code Name
1 2048 3907029000 1.8 TiB FD00 Linux RAID