HP StorageWorks Snapshot XP user guide (T1713-96023, October 2006)

Example

S2 = ↑[{4398046511104÷(256×1024)}×(32÷74784)]↑ ×74784

= ↑7178.9542...↑ ×74784

= 5368 74336

S1 = 107 3 74182 4 – 536874336 – 8 × 10242²

=528478880

Total capacity of P-VOLs (kB ) = ↑(528478880 ÷ 74784 )↑ ×16384×256

= ↑7066.737 ...↑ ×16384×256

=7067×16384×256

= 29641146368

Since the total capacity of P-VOLs is 27,648 in gigabytes, maximum number of Snapshot XP pairs will be

as follows:

MaximumnumberofSnapshotXPpairs=27648÷{↑（10÷4）↑×4}

=27648÷12

=2304

According to these results, you can create a ma ximum of 2,304 Snapshot XP pairs.

Using the num

ber of pair tables

Hitachi Flas

hCopy 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, w

hich is an Hitachi FlashCopy Mirro ring 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 HitachiShadowImageforz/OSuser

guide.

For examp

le, when the relationship expansion function is enabled and the num ber 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

Accordin

g to this result, you can create a maximum of 2,768 Snapshot XP pairs.

HP StorageWorks Snapshot XP user guide