HP XP Racks - Manual (Page 17)

• Use the following formula:
Σ(α) ≤ (β)and Σ(γ) ≤ (δ)
where:
•
Σ(α): The total number of differential tables per pair.
For more information about the total number of differential tables per pair, see “Calculating
the maximum number of BC Z pairs” (page 16) .
•
(β): The number of differential tables available in the system.
For more information about differential tables, see “Tables and installed shared memory”
(page 15) ).
•
Σ(γ): The total number of pair tables per pair (per previous calculation).
•
δ: The number of pair tables available in the system.
For more information about pair tables, see “Tables and installed shared memory”
(page 15) ).
NOTE: The value for (β) and (δ) is dependent on the amount of installed shared memory.
For more information about installed shared memory, see “Tables and installed shared memory”
(page 15) .
For example, if you are creating 10 BC Z pairs of 3390-3 volumes and twenty BC Z pairs of
3390-L volumes in a XP7 storage system that has 57,600 differential tables, use the following
equation to calculate Σ(α) and Σ(γ):
Σ(α): (3 x 10) + (24 x 20) = 510
Σ(γ): (1 x 10) + (1 x 20) = 30
Since 510 is less than 57,600, and 30 is less than 8,192, you can create 10 BC Z pairs of 3390-3
volumes and twenty BC Z pairs of 3390-L volumes.
Quick Split and Steady Split performance planning
The following dependencies affect the performance of pairs that are in the process of Quick Split
(“V-Split/SUSPVS” status) or Steady Split (“SP-Pend/TRANS” status):
•
The system option mode (SOM) 459 is ON.
•
The S-VOL is an external or internal volume.
•
The S-VOL is a volume that is part of a THP V-VOL.
The following table shows the affects of these conditions.
V-Split/SUSPVS or SP-Pend/TRANS status S-VOL SOM 459
Differential data is copied to the cache in the XP7 storage system.
The pair is in the process of Quick Split (“V-Split/SUSPVS” status). Internal volume OFF
External volume
Internal volume ON
Differential data is copied to the cache in the XP7 storage system and
destage to the external storage system has completed. The pair is split
(“Split/SUSPOP” status). External volume
* Indicates a THP V-VOL.
Quick Split and Steady Split performance planning 17