HP XP Continuous Access Software - Manual (Page 47)

Table 14 RAID Level Configuration of XP Continuous Access Journal
Support Specifications Item
RAID1, RAID5, and RAID6 can coexist. RAID configuration of the data volume and journal
volume
RAID1, RAID5, and RAID6 can coexist in the same journal group.
Maximum Number of Pairs
The number of pairs that can be created in a storage system is limited. Use the number of cylinders
and bitmap areas to calculate the maximum number of pairs that can be created in a storage
system.
•
The number of cylinders
The number of pairs of a primary data volume and a secondary data volume are limited. The
number of pairs depends on the volume capacity (that is, the number of cylinders in the volumes
that form pairs). If CVS is used, the number of pairs depends on the number of cylinders
specified by CVS. A limit on the number of pairs is applied to both the primary storage system
and the secondary storage system. Use the following formula to calculate the number of
cylinders for different emulation types:
◦ For OPEN-V:
The number of cylinders = ( ( ( (Max. LBA/512) ) /15) ) + 1
– The … symbols around a value indicate that the value should be rounded up to
the nearest integer.
– LBA: Logical Block Address. This is the capacity of volumes measured in blocks.
•
The number of required bitmap areas
The number of bitmap areas to be used by all data volumes that form pairs can be calculated
from the number of cylinders. This number is called the required number of bitmap areas. Use
the following formula to calculate the required number of bitmap areas for a data volume.
The … symbols around a value indicate that the value should be rounded up to the nearest
integer.
The required number of bitmap areas = ( ( (number of cylinders × 15) 122,752) )
◦ number of cylinders × 15 indicates the number of slots,
◦ 122,752 is the number of slots that a bitmap area can manage.
If the calculated required number of bitmap areas exceeds the total number of bitmap areas
in the storage system, the number of pairs that can be created is limited.
If you use LUSE volumes, you must add 1 to the value calculated by the formula above.
•
The maximum number of pairs that can be created
The maximum possible number of pairs that can be created is defined by the number of bitmap
areas in the storage system and the number of bitmap areas required to create pairs.
The number of bitmap areas in the storage system is defined by the capacity of shared memory.
The relationship between the capacity of shared memory and the number of bitmap areas in
the storage system is described in
Table 15 (page 48) .
Requirements and Restrictions 47