HP XP7 Storage - Manual (Page 32)

Requirements for Fast Snap tasks
You must calculate the number of FS pairs you can create. When you create FS pairs for a P-VOL
for the first time, the number of FS pairs that you can create in a storage system depends on the
following:
•
The number of FS pairs that you can create based on the number of available pair tables (see
“Calculating the number of Fast Snap pairs based on pair tables” (page 32) ).
•
The snapshot estimated manageable capacity (see “Workflow for calculating Fast Snap pairs
based on the snapshot estimated manageable capacity” (page 32) ).
•
The number of cache management devices that you must make available (see “Workflow for
calculating Fast Snap pairs based on cache management devices” (page 33) and “Calculating
the number of cache management devices” (page 33) ).
The smallest of the three calculations is the maximum number of FS pairs that you can create in
the storage system.
When you create FS pairs again, you only need to know the number of pair tables to calculate
the number of FS pairs that you can create. You do not need to know the snapshot estimated
manageable capacity or the number of cache management devices.
If you have multiple P-VOLs, calculate the number of FS pairs that you can create for each P-VOL
in the storage system.
Calculating the number of Fast Snap pairs based on pair tables
Pair tables contain information that is required to manage FS pairs. Each FS pair requires at least
one pair table. You can use up to 1,048,575 pair tables in a XP7 storage system.
1. View the number of existing FS pairs (see “Viewing local replication summary information”
(page 90) ).
2. Calculate the number of FS pairs that you will need using the following formula:
The number of FS pairs you will need based on pair tables = 1,048,575
- (the number of existing FS pairs)
Workflow for calculating Fast Snap pairs based on the snapshot estimated
manageable capacity
Use the following workflow to calculate the number of FS pairs you can create based on the
snapshot estimated manageable capacity:
1. View the snapshot estimated manageable capacity (see “Viewing local replication summary
information” (page 90) ).
2. Calculate the number of FS pairs that you can create using the following formula:
The number of FS pairs that you can create = The snapshot estimated
manageable capacity / The snapshot management capacity in a P-VOL
The snapshot estimated manageable capacity in a P-VOL = (the P-VOL
capacity of FS pairs [TB] / 2.6 [TB]) * 3,024 [GB] + (168GB * 2
(consumed SM))
Related topics
•
“Viewing the number of pairs and a list of pairs” (page 96) .
•
“Calculating the remaining shared memory” (page 32) .
Calculating the remaining shared memory
Use the following formula to calculate the remaining SM:
32 Planning and design requirements