HP XP Array Manager Software - Manual (Page 14)

a. Where the bind mode is set:
For RAID-1:
•
Required cache size = Number of addresses x (512 + 16) x 2 ÷ 1,024
The unit is KB.
For RAID type other than RAID-1:
•
Required cache size = Number of addresses x (512 + 16) x 3 ÷ 1,024
The unit is KB.
b. Where the priority mode is set:
•
Required cache size = Number of addresses x (512 + 16) ÷ 1,024
The unit is KB.
Note: If a RAID-5 or RAID-6 volume area is changed from priority mode to bind mode and no
cache is added, then only 33 percent of the user data will fit in the area previously assigned for
priority mode, and the remaining 67 percent is used to save read/write data. If a RAID-1 volume
area is changed from priority mode to bind mode and no cache is added, then only 50 percent
of the user data will fit in the area previously assigned for priority mode, and the remaining 50
percent is used to save read/write data. Changing the mode without cache extension requires a
Cache Residency reconfiguration.
Cache Requirements for Mainframe Systems
To calculate the cache size for the mainframe systems:
1. Calculate the converted values of the starting address and the ending address.
To calculate the converted values of the starting address and the ending address for the all
specified LDEVs:
•
Setting value of ending address (CC) = (
↓((LDEV size x 15) - 1) ÷ 15↓)
Round down the value that is calculated from the formula between the two downward
arrows (
↓) after the decimal point.
Setting value of ending address (CC) is the value which is input in the Cache Residency
window.
•
Setting value of ending address (HH) = ((LDEV size x 15) - 1) Mod 15
The remainder will be the setting value of ending address (HH).
Setting value of ending address (HH) is the value which is input in the Cache Residency
window.
•
Converted value of starting address = 0
•
Converted value of ending address
= Setting value of ending address (CC) x 15 + Setting value of ending address (HH)
Setting value of ending address (CC) and Setting value of ending address (HH) is the
value which is input in the Cache Residency window.
To calculate the converted values of the starting address and the ending address if the volumes
are specified:
•
Converted value of starting address
= Setting value of starting address (CC) x 15 + Setting value of starting address (HH)
14 Preparing for Cache Residency Manager Operations