HP XP Business Copy Software - Manual (Page 79)

Business Copy XP user guide for the XP10000/XP12000 79
A Maximum pair calculations
Calculating the maximum number of Flex Copy XP copy pairs
The maximum number of copy pairs that can be created using Flex Copy XP is 8,192.
CAUTION: You cannot create more copy pairs than the number of external volumes that are mapped as
internal volumes.
When a copy pair is created, differential tables are used. Differential tables are disk array resources that
are shared by Flex Copy XP, Business Copy XP, ShadowImage for z/OS, Hitachi FlashCopy Mirroring,
Hitachi FlashCopy Mirroring Version2, Snapshot XP, and Auto LUN XP. The maximum number of
differential tables that Flex Copy XP can use is the total number of differential tables in the disk array minus
the number used by other applications.
The actual number of pairs you can create depends on the following:
• How much shared memory is available for differential tables. The number of differential tables
available in a disk array is determined by whether additional shared memory for differential tables is
installed.
• You can use 13,652 differential tables if no additional shared memory for differential tables is
installed.
• You can use 30,718 differential tables if additional shared memory for differential tables is
installed.
NOTE: Contact your HP account support representative for more information about adding additional
shared memory.
• The emulation type and capacity of each volume used to create a pair:
• The maximum number of copy pairs can be smaller than 8,192 if you use large LUs to create pairs.
• The number of copy pairs that can be created depends on the emulation type of the volume,
because each emulation type requires a different number of differential tables. You must use
OPEN-V for Flex Copy XP pairs.
Calculating the required number of differential tables
Use the following equation to calculate the total number of differential tables required per pair:
, where:
• (X): Volume capacity (KB)
NOTE: 1 KB equals 1024 bytes.
• (Z): Number of slots that can be managed by a differential table (61,312)
NOTE: Round the result of the calculation up to the nearest whole number.
For example, if the volume capacity (X) is the maximum OPEN-V volume capacity of 3,019,898,880 KB,
the total number of differential tables is calculated as follows:
When you round up to the nearest whole number, the result is 193. Therefore, the total number of
differential tables for one pair is 193 when the emulation type is OPEN-V.
X 256 ÷ ( ) Z ( ) ч
3019898880 256 ч ( ) 61312 ч 192.40084 =