HP SureStore E Disk Array 12H User's and Service Manual (C5445-90901, September 1999)

Concepts and Management
Managing the Disk Array Capacity
103
Concepts
Capacity Management Strategies
The way you decide to configure your disk array capacity will be determined by your system needs and
your disk array management strategy. Are you willing to sacrifice maximum protection against disk failure
for increased capacity? Is performance an issue?
Table 3 describes the steps you can take to achieve your primary goal in managing the disk array. The
trade-offs associated with each strategy are also described.
Table 3. Disk Array Management Strategy
To optimize... You should...
But be aware that...
Capacity
•
Make sure all capacity is allocated to
logical drives. Do not leave any capacity
unallocated.
•
Avoid using Active Hot Spare, thus
freeing up more capacity for logical
drives.
•
Disabling Active Hot
Spare to increase the
available capacity has the
disadvantage of reducing
protection from multiple
disk failures.
Disk Array
Performance
•
Leave some capacity unallocated for use
as RAID 0/1 space. This maintains
performance as your disk array begins to
reach its maximum storage capacity.
•
Keep Active Hot Spare Enabled to
maintain performance following a disk
failure. Because performance suffers
when the disk array is operating in
critical or non-redundant mode,
rebuilding quickly will maintain disk
array performance. The array also uses
the Active Hot Spare as RAID 0/1 space
until needed.
•
Leaving capacity
unallocated and enabling
Active Hot Spare both
reduce the amount of
capacity available to the
operating system.
Data Redundancy
•
Leave Active Hot Spare and Auto
Rebuild enabled. This offers the best
protection from a disk failure.
•
Enabling Active Hot
Spare decreases the
amount of capacity
available to the host.