HP StorageWorks XP Remote Web Console Software User Manual
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Guide: HP XP24000 Disk Array, HP XP20000 Disk Array. For information about how to calculate
the number of differential tables and pair tables that are required for XP Auto LUN, see the HP
XP24000/XP20000 Auto LUN Software User Guide. See the HP XP24000/XP20000 Snapshot
User Guide to calculate the number of differential tables that are required for XP Snapshot.
Assuming that only Version 1 uses differential tables and pair tables, this section describes:
•
How to calculate the number of differential tables and pair tables required for one Version 1
relationship
•
The conditions you need to consider when calculating the number of Version 1 relationships
that can be created
Use the following expression to calculate the total number of differential tables per relationship
Total number of the differential tables per relationship = ((X) + (Y)) x 15
(Z)
(X): The number of cylinders in the volume.
(Y): The number of control cylinders (see
).
(Z): 20,448 (the number of slots that can be managed by a differential table).
: Round up the number.
Round up to the nearest whole number. For example, if a volume has an emulation
type of 3390-3 and the number of cylinders in the divided volume is 3,390 ((X) in
the previous expression), the calculation of the total number of differential tables
is:
(3,339 + 6) × 15
20,448 = 2.4537...
When you round 2.4537 up to the nearest whole number, it becomes 3. Therefore,
the total number of differential tables for one relationship is 3 when the emulation
type is 3390-3.
You can use 36 differential tables per pair table. Therefore, the total number of
pair tables is 1 when the emulation type is 3390-3. For example, in the case of a
volume whose emulation type 3390-M, and the number of cylinders in the volume
is the default value, the number of pair tables is 2. However, only the emulation
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Preparing for Version 1 Operations