Hewlett Packard Enterprise HPE XP7, User Manual, Page: 70 / 311

floor( ): Truncates the value calculated from the formula in parentheses after the decimal point.
Estimate pool-VOL capacity in multiples of 42 MB. Specifying a pool-VOL capacity in other multiples less
than 42 MB truncates the fraction.
If you install THP/Smart/FS Extension in the shared memory, the available pool capacity per P-VOL is
768 TB, and the total capacity of all pools is 12.3 PB.
More information
Calculating the number of Fast Snap pairs based on pair tables on page 64
Calculating Fast Snap pairs based on the snapshot estimated manageable capacity on page 64
Calculating Fast Snap pairs based on cache management devices on page 65
Calculating the number of cache management devices on page 66
Calculating the Fast Snap pair capacity for THP pools on page 66
External Storage and external volumes used as pool-VOLs on page 71
Simultaneous processing of multiple Fast Snap pair tasks on page 71
Pair operations when pairs are cascaded on page 72
Pair operations when pairs are not cascaded on page 83
Pair operations when a P-VOL is shared by multiple S-VOLs on page 84
Data recovery and backup differences between Fast Snap and Business Copy on page 85
Fast Snap cache management device requirements on page 68
Fast Snap shared memory requirements on page 56
Resolving insufficient pool capacity
Make sure you have sufficient pool capacity. If the pool capacity is insufficient, the storage system can
suspend Fast Snap pairs ("PSUE" status).
NOTE: When the setting, Suspend FS pairs when depletion threshold is exceeded , is set to Yes in
RWC or in RAID Manager by uisng the command,
raidcom modify pool -suspend_tipair
<yes>
for a THP pool, the status of FS pairs using the pool might change to PSUE if the depletion
threshold is exceeded. When it is set to No in RWC or in RAID Manager by uisng the command,
raidcom modify pool -suspend_tipair <no>
for an FS pool or a THP pool, the status of FS
pairs using the pool might change to PSUE if the pool becomes full.
Procedure
1. Estimate the capacity of snapshot data to be copied to the pool.
If the capacity of snapshot data to be copied to the pool varies hour by hour, ensure that the largest
capacity is your pool capacity.
2. Assign the pool capacity based on the estimate.
Pool capacity calculations
Use the following formula:
Capacity of snapshot data to be copied =
Capacity of data written to the same area in the P-VOL during the period
from when snapshot data is stored to when the snapshot data is deleted
Although the pool capacity is decided according to the estimation, if the pool capacity exceeds the
threshold, address the issue.
70 Resolving insufficient pool capacity