HP D3000 Disk Enclosures - Manual (Page 24)

After the rebuild of the data onto the spare is completed, when a replacement drive is inserted to
replace the failed drive, the system will automatically transfer the data from the spare onto the
replacement drive and return the spare to an available-spare state. It is important to note that the
process of rebuilding the spare or the replacement drive must not be interrupted or the process will
be aborted.
Some administrators have multiple spare disks, so that multiple arrays can experience failure and
successfully recover, before administrative intervention would be required to replace the spare or
failed disk. When assigning a spare to an array, the administrator chooses which arrays and how
many arrays are protected by that spare.
Array sizing
As a general rule, the greater the number of drives that are included in an array, the greater the
performance level that can be achieved. However, performance considerations are offset by fault
tolerance considerations. The greater the number of drives in an array, the higher the probability
of one or more disk failures in that array. The administrator must strike a balance between
performance and fault tolerance.
24 Installation