HP StorageWorks P9000 - Disk Arrays User Manual page 5

Before partitioning cache memory into CLPRs, calculate how much cache capacity will be needed
on your storage system, and then install any needed additional cache memory. It will be difficult
to add more cache memory after partitioning cache into CLPRs.
To determine whether you need additional cache capacity, see the following table and formulas.
The recommended cache capacity for an internal volume is determined by the storage capacity
assigned to the cache logical partition.
Table 1 CLPR data capacity and recommended cache capacity
CLPR data capacity
Less than 2,900 GB
2,900 GB or more
14,400 GB or more
128,000 GB or more
182,000 GB or more
218,000 GB or more
254,000 GB or more
290,000 GB or more
326,000 GB or more
To calculate CLPR data capacity:
Data capacity = number of 3D+1P parity groups x capacity of one HDD x 3 + number of 6D+2P
parity groups x capacity of one HDD x 6 + number of 7D+1P parity groups x capacity of one
HDD x 7 + number of 2D+2D parity groups x capacity of one HDD x 2
To calculate the cache capacity for a CLPR:
cache capacity (GB) = recommended cache capacity (GB) + ceiling (Cache Residency capacity
(MB) / 2,048) x 2 GB
When you use an external volume or a virtual volume, you cannot use the above formula. If you
use an external volume, calculate the capacity of parity group that is associated to the CLPR, and
then calculate the cache capacity according to the data capacity and the recommended capacity
in the above table. If you use a virtual volume, calculate the total LDEV capacity of the virtual
volume that is associated to the CLPR, and then calculate the cache capacity according to the data
capacity and the recommended capacity in the above table. To check the LDEV capacity of the
virtual volume, see the LDEV dialog box in the Reports Display dialog box of the Remote Web
Console subwindow. For further information about Remote Web Console subwindow, see the HP
StorageWorks P9000 Remote Web Console User Guide.
When adding cache memory, use either the Standard Cache Access Model mode or the High
Performance Cache Access Model mode. If your storage system has any additional printed circuit
boards (PCBs), you must use the High Performance Cache Access Model mode. For more information
about adding cache memory, contact HP Technical Support.
Processor blade
2
4
6
8
2 or 4
6
8
2, 4 or 6
8
2, 4, 6 or 8
Recommended cache capacity
8 GB or more
16 GB or more
24 GB or more
32 GB or more
16 GB or more
24 GB or more
32 GB or more
24 GB or more
32 GB or more
32 GB or more
40 GB or more
48 GB or more
56 GB or more
64 GB or more
72 GB or more
About virtual cache partitions 5