How many hot spares you should have

At a minimum, you should have at least one matching or appropriate hot spare available for each kind of disk installed in your storage system. However, having two available hot spares for all disks provides the best protection against disk failure.

Having at least two available hot spares for all disks provides the following benefits:

• At least two hot spares must be available in order to put a disk into the maintenance center.
• Having two hot spares means that when a disk fails, you still have a spare available if another disk fails before you replace the first failed disk.