Calculating maximum number of pairs, 8 additional shared memory for differential tables – HP StorageWorks XP Remote Web Console Software User Manual
Page 42
Calculating Maximum Number of Pairs
When you create Business Copy pairs, resources called differential tables and pair tables will be
required. The number of available differential tables and pair tables in one storage system depends on
whether additional shared memory is installed or not.
on page 42 shows the differential and pair
tables that are supported by the options for adding shared memory.
Table 8 Additional Shared Memory for Differential Tables
Additional Shared Memory
for Business Copy
Num. of
Differential Tables
Num. of Pair Tables Num. of Volumes
in Storage system
No additional shared memory
for Business Copy
0
0
1,024
Additional shared memory for
Business Copy is installed
26,176
8,192
16,384
Extension 1
57,600
8,192
16,384
Extension 2
104,768
16,384
65,536
Extension 3
146,688
16,384
131,072
Extension 4
209,600
16,384
131,072
Notes:
•
To install additional shared memory for differential tables, call HP technical support.
•
Even if you install additional shared memory for differential tables and pair tables, the
maximum number of pairs is half of the total number of volumes in the storage system (see
on page 42). For example, if additional shared memory for Business Copy is installed
(second line in
on page 42), and when P-VOLs and S-VOLs are in a one-to-one
relationship, you can create up to 8,192 pairs. However, note that in case of Extension 2 to
Extension 4, the maximum number of pairs is 16,384, regardless of the total number of volumes
in the storage system.
To calculate the maximum number of Business Copy pairs, first you need to calculate how many
differential tables and pair tables are required to create Business Copy pairs, and then compare the result
with the number of differential tables and pair tables in the whole storage system. Note that in addition
to Business Copy, the following program products will also use differential tables and pair tables.
•
Program products using differential tables
• ShadowImage for Mainframe
• Compatible FlashCopy Version 1
• Compatible FlashCopy Version 2
• Auto
LUN
• XP Snapshot
•
Program products using pair tables
• ShadowImage for Mainframe
• Compatible FlashCopy Version 1
• Auto
LUN
If Business Copy and these program products are used in the same storage system, the number of
available differential and pair tables for Business Copy pairs will be the total number of available tables
in the storage system minus the tables used by the above program products.
For information about how to calculate the number of differential tables and pair tables that are required
for ShadowImage for Mainframe, see the Hitachi ShadowImage for z/OS User’s Guide. For Compatible
FlashCopy Version 1 and Compatible FlashCopy Version 2, see the HP StorageWorks XP24000 for
FlashCopy Mirroring Software User’s Guide. Also, see the HP StorageWorks XP Auto LUN Software
User's Guide to calculate the number of differential tables and pair tables that are required for Auto LUN,
42
Preparing for Business Copy Operations