I am using Redhat 9.0 with:

2 SCSI disk as system disk /dev/md0 (Raid1)
2 IDE as data disk /dev/md1 (Raid-1) [/dev/hda1 /dev/hdc1]
2 IDE as data disk /dev/md2 (Raid-1) [/dev/hdb1 /dev/hdd1]

There were bad contact on some IDE cable before, which causes /dev/hdc1 and /dev/hdb1 offline for a while.

There are useful data on /dev/hda1 and /dev/hdd1. The machine is still running fine.

From /proc/mdstat, it shows:
Personalities: [raid1]
read_ahead 1024 sectors
md2: active raid1 hdd1[1]
117218176 blocks [2/1] [_U]

md1: active raid hda1[0]
117218176 blocks [2/1] [U_]

md0: active raid1 sdb2[1] sda[0]
3882944 blocks [2/2] [UU]

1. Can anybody tell me how to read the status output above? What are those [?/?] [UU] mean?

2. How can I rebuild the array (re-active /dev/hdc1 /dev/hdb1) and keep the data from the good disks?

3. From some forum, they talk about a utility call ckraid, but I cannot find it in Redhat 9? Do I need this utility?

4. I find mdadm from some ftp site. Can I use this utility to rebuild the array without destory the data? How?

Thanks in advance.

Mike