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How much modified (write) data will the snapshots have?
Of the snapshots
that will be mounted as read-write and actually written to, factor in the
average amount of data that will be modified.
Add 750 Mbyte of reserve space for internal use.
Add a recommended 25% safety margin to the snap pool in case actual capacity
use exceeds the estimate.
You can estimate snap-pool size as shown in following example. Assume you want
to create a snap-pool for two 10-Gbyte master volumes, and will use these values:
Master volume size = 10,000 Mbyte
Average percent of change = 5% (0.05)
Number of snapshots retained = 4
Number of modified snapshots = 4
Average write data = 1,000 Mbyte
Snap-pool reserve space = 750 Mbyte
Safety margin = 25%
The snap-pool size calculation is:
Therefore, the snap pool should be approximately
16,000 Mbyte
(16 Gbyte).
If you cannot estimate the size values, you can specify a reasonable initial
size and use the Auto Expand policy to expand the snap pool when it reaches a
capacity threshold. See “Setting Snap Pool Policies and Thresholds” on page 110.
For an explanation of sizes represented by various units, see “Size
Representations in SMU” on page 27 for more information.
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