Monitoring used pool capacity and used pool capacity reserved for writing
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Monitoring used pool capacity
The used pool capacity must always be monitored. As data is written to DP-VOLs and stored in the pool, in cases where DP-VOLs are over-provisioned, the pool might become full before the DP-VOLs become full. Therefore, the used pool capacity must always be monitored to prevent this from happening. A threshold value is set for the used pool capacity. If the used pool capacity exceeds the threshold value, a SIM is reported and a notification is sent to the hosts. If these SIMs are reported, you can resolve the status of threshold exceeded by expanding the pool capacity or by deleting data. For details about the threshold values, see Thresholds for monitoring pools.
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Monitoring used pool capacity reserved for writing
For the pools consisting of pool volumes carved from accelerated compression-enabled parity groups, you must monitor both the used pool capacity and the used pool capacity reserved for writing. If the used pool capacity reserved for writing exceeds the threshold value, a SIM is reported. The used pool capacity and the pool capacity reserved for writing are not always the same, and the SIMs are independent of each other. The following conditions can occur:
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The used pool capacity exceeds the threshold, but the used pool capacity reserved for writing is lower than the threshold.
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The used pool capacity is lower than the threshold, but the used pool capacity reserved for writing exceeds the threshold.
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Both used capacities exceed the threshold.
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If SIMs are reported, you can resolve the status of the exceeded threshold by expanding the pool capacity or by deleting unwanted data.
If pool volumes that are carved from accelerated compression-enabled parity group are used to create a new pool, you must estimate the data savings percentage beforehand.
For a pool with a pool volume that has accelerated compression enabled, the used pool capacity and the used pool capacity reserved for writing are monitored. The following shows the threshold values for the used pool capacity and used pool capacity reserved for writing that trigger output of SIMs when exceeded:
- Warning Threshold: You can set a value from 1% to 100% in 1% increments. The initial value is 70%.
- Depletion Threshold: You can set a value from 1% to 100% in 1% increments. The initial value is 80%.
- Prefixed Depletion Threshold: The value is set for the used capacity of the parity group. The value is fixed at 90%.
The following figure shows the used pool capacity and used pool capacity reserved for writing with threshold values. Hereinafter, the smaller free capacity between the pool or drive is called the remaining free capacity reserved for writing. The used capacity reserved for writing is the result of deducting the remaining free capacity for writing from the total capacity reserved for writing.
