Ubuntu Servers :: Create A New Mdadm RAID 5 Device /dev/md0 Across Three Disks?

I am trying to create a new mdadm RAID 5 device /dev/md0 across three disks where such an array previously existed, but whenever I do it never recovers properly and tells me that I have a faulty spare in my array. More-specific details below. I recently installed Ubuntu Server 10.10 on a new box with the intent of using it as a NAS sorta-thing. I have 3 HDDs (2 TB each) and was hoping to use most of the available disk space as a RAID5 mdadm device (which gives me a bit less than 4TB.)

I configured /dev/md0 during OS installation across three partitions on the three disks - /dev/sda5, /dev/sdb5 and /dev/sdc5, which are all identical sizes. The OS, swap partition etc. are all on /dev/sda. Everything worked fine, and I was able to format the device as ext4 and mount it. Good so far.

Then I thought I should simulate a failure before I started keeping important stuff on the RAID array - no point having RAID 5 if it doesn't provide some redundancy that I actually know how to use, right? So I unplugged one of my drives, booted up, and was able to mount the device in a degraded state; test data I had put on there was still fine. Great. My trouble began when I plugged the third drive back in and re-booted. I re-added the removed drive to /dev/md0 and recovery began; things would look something like this:

Code:
user@guybrush:~$ cat /proc/mdstat
Personalities : [linear] [multipath] [raid0] [raid1] [raid6] [raid5] [raid4] [raid10]
md0 : active raid5 sdc5[3] sdb5[1] sda5[0]
3779096448 blocks level 5, 64k chunk, algorithm 2 [3/2] [UU_]

[Code]...