HP StorageWorks XP Remote Web Console Software - Manual (Page 27)

Example
S2 = ↑[{ 4398046511104 ч (256 Ч 1024)} Ч (32 ч 74784)]↑ Ч 74784
= ↑7178.9542...↑ Ч 74784
= 536874336
S1 = 1073741824 – 536874336 – 8 × 10242²
= 528478880
Total capacity of P-VOLs (kB) = ↑(528478880 ч 74784 )↑ Ч 16384 Ч 256
= ↑7066.737...↑ Ч 16384 Ч 256
= 7067 Ч 16384 Ч 256
= 29641146368
Since the total capacity of P-VOLs is 27,648 in gigabytes, maximum number of Snapshot XP pairs will be
as follows:
Maximum number of Snapshot XP pairs = 27648 ч {↑（10 ч 4）↑Ч4}
= 27648 ч 12
= 2304
According to these results, you can create a maximum of 2,304 Snapshot XP pairs.
Using the number of pair tables
Hitachi FlashCopy Mirroring Version 2 and Snapshot XP pairs use pair tables to store control information
needed to manage pairs. To create an Hitachi FlashCopy Mirroring Version 2 or Snapshot XP pair,
you need one pair table for each pair.
Usually, up to 32,768 pair tables are available in one array. However, if the relationship expansion
function, which is an Hitachi FlashCopy Mirroring Version 2 function, is enabled, the maximum number of
available pair tables in one array is 1,048,575.
Among array software products, only Hitachi FlashCopy Mirroring Version 2 and Snapshot XP use pair
tables. Therefore, if you use Hitachi FlashCopy Mirroring Version 2, calculate the number of available
pair tables for Snapshot XP pairs by subtracting the number of differential tables Hitachi FlashCopy
Mirroring Version 2 pairs use from the number of pair tables for the whole array.
For information about checking the number of pair tables Hitachi FlashCopy Version 2 uses (that is, the
number of existing Hitachi FlashCopy Version 2 pairs), see the Hitachi ShadowImage for z/OS user
guide.
For example, when the relationship expansion function is enabled and the number of pair tables Hitachi
FlashCopy Mirroring Version 2 uses is 30,000, calculate the number of Snapshot XP pairs you can
create for an array as follows.
32,768 - 30,000 = 2,768
According to this result, you can create a maximum of 2,768 Snapshot XP pairs.
HP StorageWorks Snapshot XP user guide 27