The failure of a Hard Disk within an Array will cause the Array to become “Degraded”.
The failed disk will be marked as “Offline” within the RAID BIOS.
It is always worth trying to force the disk back “Online” before trying anything else.
If this doesn’t work, replace the faulty Drive ASAP with a brand new drive (of equal or larger capacity), and the array will re-build automatically. If you have a “Hot Swap” chassis, you can do this whilst the server is running.
Replacing the faulty disk with one that has been previously used in another array, will cause the new drive to show up as “Foreign”. In this circumstance, you will need to “Clear” the Foreign Array before you can use it: Foreign Config => Clear. It is always simpler to use a brand new drive.
DO NOT select “Clear Config” from the Main Operations Menu, or you will destroy all of the data on your Array!
Note: RAID 0 has no redundancy built in, and so cannot survive the loss of even a single disk. You will need to restore the entire system from Backups in this scenario.