Please help - Ubuntu RAID with mdadm

[S2267]

Hello everybody,

I am experiencing a strange behavior with software RAID5 in Ubuntu 12.10.

I created a RAID5 device with 3 x 2TB disks (capacity 4 TB + spare).
I added a forth 2TB drive, same model and used mdadm --add to add it to the existing RAID5.

Now, it I execute a mdadm --detail on the md drive I get:

-----------------------------------------------------------------------
/dev/md0:
Version : 1.2
Creation Time : Fri Mar 15 20:52:54 2013
Raid Level : raid5
Array Size : 5860141056 (5588.67 GiB 6000.78 GB)
Used Dev Size : 1953380352 (1862.89 GiB 2000.26 GB)
Raid Devices : 4
Total Devices : 4
Persistence : Superblock is persistent


Intent Bitmap : Internal


Update Time : Sun Mar 24 10:24:56 2013
State : active
Active Devices : 4
Working Devices : 4
Failed Devices : 0
Spare Devices : 0


Layout : left-symmetric
Chunk Size : 512K


Name : Hulk:0 (local to host Hulk)
UUID : 4db896f2:38b1dfc5:3552ef0c:92418427
Events : 125988


Number Major Minor RaidDevice State
0 8 97 0 active sync /dev/sdg1
1 8 113 1 active sync /dev/sdh1
3 8 145 2 active sync /dev/sdj1
4 8 129 3 active sync /dev/sdi1
-----------------------------------------------------------------------


It seems like all four drive are correctly seen by the system.
But I believe I should see a total capacity (Array Size) of 8 TB (with Used Dev Size of 2TB) right?

The RAID is mounted under /var?raid and df show a total capacity of 4TB (as it was before I added the 4th drive).

Any idea?


Whan I do a

mdadm --grow /dev/md0 --raid-devices=4
it says

mdadm: /dev/md0: no change requested


I tried to google for smilar problem, but couldn't find any solution.

I hope somebody could head me to a solution.

Thank you.
Stefano

[darkod]

I think the array size is correct at 6TB since it doesn't count the parity disk in raid5 (the fourth disk). The Used Dev size looks correct at 2TB since I think that shows the parity capacity.

As for what df shows (4TB) you probably only need to extend the filesystem. Unmount /dev/md0 and try something like:

sudo resize2fs /dev/md0

That should extend it to the max size.

[S2267]

Darko, a huge

THANK YOU!!!

I thought mdadm took also care of expanding the md partition.
I was lost for a few hours before posting my message and you solved my problem in 20 minutes.
Amazing. Thanks a lot again.
Stefano