Setting Alert Threshold
To monitor the amount of pool space allocated in dynamic pools, you can set an alert threshold which will post an alarm in the event log (and shows up in the Alarms tab) if storage units go above the threshold. The alert does not apply for static pools because storage is fully allocated when created.
Set the alert threshold in the Managed Volumes tab in SANmanager. Select a pool and choose Properties from the context menu. Enter the threshold in the Pool Settings dialog box.
The Alert Capacity Threshold is a percentage, and the default is 80%. When the pool allocation rises above the Alert Capacity Threshold (aka watermark), an event will be posted in the System Event Log:
DcsVlv,21: Warning: The allocation percentage of NMV pool {b2abff26-6a83-11db-b019-0007e923535f} is 81 and has reached or exceeded the low watermark. You should assign more disks to the NMV pool to avoid failing writes. You will not be able to create new NMVs from this pool.
This in turn triggers an alarm in the SANcentral Alarms tab.
Be sure to add more physical disks to your pools when you receive the message that the pool is reaching the low watermark. As with traditional storage, when the pool is depleted you will not be able to create new NMVs from pools or write I/Os until free storage resources are available. If you fail to do this, you will next see another error message informing you that a new storage unit failed to allocate because the NMV pool is empty. You will need to assign new disks to the pool to resolve the problem. When more physical storage is added to the pool, capacity growth occurs transparently to the application server user.