If i type : mdadm --detail /dev/md0
Then i'll get:
----------------------------------------
/dev/md0:
Version : 1.2
Creation Time : Tue May 24 20:47:56 2011
Raid Level : raid1
Array Size : 96244 (94.00 MiB 98.55 MB)
Used Dev Size : 96244 (94.00 MiB 98.55 MB)
Raid Devices : 3
Total Devices : 2
Persistence : Superblock is persistent

Update Time : Sat Apr 14 17:29:49 2012
State : clean, degraded
Active Devices : 2
Working Devices : 2
Failed Devices : 0
Spare Devices : 0

Name : zeus:0
UUID : d76edb30:3e9ff595:2a0a18dd:24931800
Events : 1744

Number Major Minor RaidDevice State
0 8 1 0 active sync /dev/sda1
1 8 17 1 active sync /dev/sdb1
2 0 0 2 removed
----------------------------------------
/proc/mdstat file:

Personalities : [raid1]
md2 : active raid1 sda3[0] sdb3[1]
241169272 blocks super 1.2 [2/2] [UU]

md1 : active raid1 sda2[0] sdb2[1]
3905524 blocks super 1.2 [2/2] [UU]

md0 : active raid1 sda1[0] sdb1[1]
96244 blocks super 1.2 [3/2] [UU_]

----------------------------------------
How can I make the "degraded" status to become normal "clean"?

Thnx in advance!

You didn't mention which OS you're using?

Anyways, if you're sure that the faulty partition or drive is OK, then you can try re-adding the partition/drive again -

whatever-partition/drive - sda, sdb, whatever is yours.

Hello - the OS that I'm using is Debian.

But the weird part of the whole post is that i don't have any other partitions to add on md0.
So i don't understand why mdadm says "removed".

You don't have to add extra partition, I didn't mention to add another partition. I'm asking you to re-add the same partition mounted on /dev/md0, which shows State : clean, degraded.

1 members found this post helpful.

Thnx - i'll give it a try...

Unfortunately: mdadm: Cannot open /dev/sdb1: Device or resource busy
(it's my boot partition)

You can also refer to this link also, http://www.iceteks.com/articles.php/linuxmdadmraid/3