Tips for Providing Hot Spare Coverage

You can use a for additional data protection from disk drive failures that occur in a , , , or . If the hot spare disk drive is available when a disk drive fails, the uses data to reconstruct the data from the failed disk drive to the hot spare disk drive. When you have physically replaced the failed disk drive, a operation occurs from the hot spare disk drive to the replaced disk drive. If you have designated the hot spare disk drive as a permanent member of an array, the copyback operation is not needed. Your storage subsystem remains online and accessible while you are replacing the failed disk drive, because the hot spare disk drive is automatically substituted for the failed disk drive.

What are some considerations for hot spare disk drive capacity?

Select a disk drive with a capacity equal to or greater than the total capacity of the disk drive that you want to make redundant with the hot spare. For example, if you have an 18- GB disk drive with configured capacity of 8  GB, you could use a 9 -GB or larger disk drive as a hot spare. Generally, do not assign a disk drive as a hot spare unless its capacity is equal to or greater than the capacity of the largest disk drive on the storage subsystem.


Note:

If hot spares are not available that have the same physical capacity, a disk drive with lower capacity may be used as a hot spare if the “used capacity” of the used disk drive is the same or smaller than the lower capacity hot spare.

How many hot spare disk drives can you create?

If you used the automatic configuration function, the storage management software creates one hot spare disk drive for every 30 disk drives of a particular . If you configured your storage subsystem manually, you can create global hot spare disk drives that are used among the arrays in your storage subsystem. The global hot spare disk drives must be equal to or greater than the capacity of the largest disk drive in the . The recommended number of global hot spare disk drives is two for each disk drive set in the storage subsystem.