Centos5.5 raid1 error and Re-Sync

Today, the system checks the status of raid1 and finds degraded, because raid1 samba is still accessible. So I opened the chassis and checked the hard drive connection line and re-plugged the power cord.
Post self-check to another hard disk.
1. [root @ zh888 ~] # Mdadm-D/dev/md0
/Dev/md0:
Version: 0.90
Creation Time: Fri Sep 2 10:33:19 2011
Raid Level: raid1
Array Size: 78150656 (74.53 GiB 80.03 GB)
Used Dev Size: 78150656 (74.53 GiB 80.03 GB)
Raid Devices: 2
Total Devices: 1
Preferred Minor: 0
Persistence: Superblock is persistent
Update Time: Tue Sep 6 11:57:19 2011
State: clean, degraded
Active Devices: 1
Working Devices: 1
Failed Devices: 0
Spare Devices: 0
UUID: 57319c2a: 090717a6: 92042ec3: e00720c4
Events: 0.52
Number Major Minor RaidDevice State
0 3 64 0 active sync/dev/hdb
1 0 0 1 removed // actually/dev/hdd is lost.
 
2. mdadm/dev/md0-a/dev/hdb // Add/dev/hdd to the/dev/md0 device again, then wait until raid1 is synchronized to the clean state. To view the synchronization progress, use cat/proc/mdstat.
[Root @ zh888 ~] # Mdadm-D/dev/md0 // The synchronization is completed.
/Dev/md0:
Version: 0.90
Creation Time: Fri Sep 2 10:33:19 2011
Raid Level: raid1
Array Size: 78150656 (74.53 GiB 80.03 GB)
Used Dev Size: 78150656 (74.53 GiB 80.03 GB)
Raid Devices: 2
Total Devices: 2
Preferred Minor: 0
Persistence: Superblock is persistent
Update Time: Thu Sep 8 08:56:31 2011
State: clean
Active Devices: 2
Working Devices: 2
Failed Devices: 0
Spare Devices: 0
UUID: 57319c2a: 090717a6: 92042ec3: e00720c4
Events: 0.770
Number Major Minor RaidDevice State
0 3 64 0 active sync/dev/hdb
1 22 64 1 active sync/dev/hdd

Author: "There is a will !"