HP XP7 Storage - Manual (Page 26)

must be subtracted from 65,536, with the difference used to calculate the maximum
number of pairs for Continuous Access Journal.
◦ If Continuous Access Synchronous and Continuous Access Journal share the same volume,
you must use the total number of bitmap areas for both pairs regardless of whether the
shared volume is primary or secondary.
•
The maximum number of pairs supported per storage system, which is 65,280. If RAID Manager
is used, it is 65,279.
Calculate the maximum number of pairs using the following formula.
Maximum number of pairs = floor( Number of bitmap areas / required
number of bitmap areas )
If the calculated maximum number of pairs exceeds the total number of LDEVs, and the total LDEVs
are less than 32,768, then the total LDEV number is the maximum number of pairs that can be
created.
Maximum initial copy operations and priorities
During configuration, you specify the maximum number of initial copies that can be run at one
time. The system allows up to 2048 initial copies to run concurrently. You do this for performance
reasons (the more initial copies running concurrently, the slower the performance).
You will also specify the priority for each initial copy during the create pair operation. Priority is
used when you are creating multiple initial copies during an operation. Creating multiple initial
copies in one operation is possible because you can specify multiple P-VOLs and S-VOLs in the
Paircreate dialog box. The pair with priority 1 runs first, and so on.
When you create more pairs than the maximum initial copy setting, the pairs with priorities within
the maximum number specified run concurrently, while the pairs with priorities higher than the
maximum number wait. When one pair completes, a waiting pair begins, and so on.
If you perform a pair operation for multiple pairs (for a specific kind of data, for example), and
then perform another operation for multiple pairs (for another specific kind of data, for example),
the pairs in the first operation are completed in the order of their assigned priorities. The system
begins processing pairs in the second set when the number of pairs left in the first set drops below
the maximum number of initial copy-setting. This is shown in the following example.
26 Planning volumes, XP7 systems