Hi, I hope someone can help. Just started to play with software RAID on Centos 3.5 and was trying to simulate a faulty drive by using the -f switch on mdadm to mark the partition (drive) as faulty and I then I removed and readded the drive, which quit happily rebuilt according the /proc/mdstat and the output from the --detail switch of mdadm. After all this mucking around I shutdown the system and tried to restart it in the morning but the system now won't boot, it gets as far as "GRUB loading" and just stops I have hard reset to get it to reboot. I have rebooted using the install CD in rescue mode and I can see that all the arrays are setup quite happily (all RAID 1's if it matters) and mdstat reports the status as "dirty,no-errors". Is that status normal? all the how-tos I've seen about software RAID show this as the status, so I have kind of assumed that is okay. Given that all the data is readable from the arrays, I'm guessing that I had to do something to GRUB prior after rebuilding the arrays and before shutting down the system. Can anyone help fill in the gap in my knowledge as to what I should have done? Thanks for any help. Regards Lee