3PAR InForm® OS 2.2.4 Concepts Guide (320-200085 Rev B, March 2009)

8.14
Virtual Volume Types and Variations
3PAR InForm OS Concepts Guide InForm OS Version 2.2.4
` Set the allocation warning and limit thresholds based on the growth rate and how much
advance warning you require before the volume reaches its limit and writes fail.
Use the following formula to generate the allocation warning threshold:
where the value of n is as follows:
◆ For a TPVV without read-only snapshots, and when that TPVV is not used for Physical
Copy or Remote Copy, n=1.
◆ For a TPVV with read-only snapshots, or when that TPVV is used for Physical Copy or
Remote Copy operations, n=2.
For example, if a 1 TB TPVV with read-only snapshots has a maximum write rate of 1 GB per
day and you would like 30 days warning prior to that TPVV reaching the allocation limit,
use the following calculation for the allocation warning percentage:
n write rate warning period
volume’s virtual size
Allocation warning = 1 —
••
percentage
•
100
2 1 GB per day
1024 GB
Allocation warning = 1 —
••
30 days
=
94 %
•
100
percentage