HP StorageWorks XP Remote Web Console Software - Manual (Page 66)

The number of resources to be used per relationship is the total number of the resources of
the copy source and copy target. For example, in the case of a volume with emulation type
3390-3, if the number of cylinders of the divided volume is 3,390 ((X) in the expression that
calculates the total number of the resource), the calculation of the total number of the differential
table is as follows:
Copy source: (3,339 + 6) Ч 15 (639 Ч 32) = 2.45379 = 3
Copy target: (3,339 + 6) Ч 15 (639 Ч 32) = 2.45379 = 3
When you round up 0.81836 to the nearest whole number, it becomes 1. Therefore, the total
number of resources to be used for one relationship is 6 when the emulation type is 3390-3.
When volumes differ in emulation type and capacity, the number of relationships that can be
established is determined according to the following condition.
NOTE: For details about the calculation of the total number of resources to be used per
relationship, see the previous expression.
The maximum number of relationships that can be established is the largest number that meets
the equation, ( ) ( ), where:
◦ ( ) means the total number of resources used per relationship
◦ ( ) means the total number of resources available in the storage system
( ) = 26,176 or 57,600 or 104,768.
If the storage system is an XP24000 Disk Array, ( ) =) can also be 146,688 or 209,600.
For details, see “Additional Shared Memory for Differential Tables” (page 15) .
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Establishing relationships by dataset copying
To establish relationships between extents, the number of required resources is the same as
the number of resources used per relationship, provided that no extents in the same volume
overlap. If the extents used for establishing the relationships overlap, the number of resources
required to establish the relationships is the number of resources to be used multiplied by the
number of extents that overlap.
“Copying Data in Two Extents that Do Not Overlap (One T-VOL)” (page 66) through “Copying
One Extent to Another in the Same Volume” (page 68) show differences in dataset copying
when the extents overlap or do not overlap. For information about the calculation example of
the resources used, see
“Referential Examples for Calculating the Number of Resources Required
to Create Version 2 Relationships” (page 68) .
Figure 32 Copying Data in Two Extents that Do Not Overlap (One T-VOL)
66 Preparing for Version 2 Operations