Negative values occur in the 'predicted pool utilizations', when some files are 'ill-placed'

A scenario where an ill-placed files may cause GPFS to produce a 'Predicted Pool Utilization' of a negative value and the course of action that you can take to resolve this issue.

This is a hypothetical situation where ill-placed files can cause GPFS to produce a 'Predicted Pool Utilization' of a negative value.

Suppose that 2 GB of data from a 5 GB file named abc, that is supposed to be in the system storage pool, are actually located in another pool. This 2 GB of data is said to be 'ill-placed'. Also, suppose that 3 GB of this file are in the system storage pool, and no other file is assigned to the system storage pool.

If you run the mmapplypolicy command to schedule file abc to be moved from the system storage pool to a storage pool named YYY, the mmapplypolicy command does the following:
  1. Starts with the 'Current pool utilization' for the system storage pool, which is 3 GB.
  2. Subtracts 5 GB, the size of file abc.
  3. Arrives at a 'Predicted Pool Utilization' of negative 2 GB.

The mmapplypolicy command does not know how much of an 'ill-placed' file is currently in the wrong storage pool and how much is in the correct storage pool.

When there are ill-placed files in the system storage pool, the 'Predicted Pool Utilization' can be any positive or negative value. The positive value can be capped by the LIMIT clause of the MIGRATE rule. The 'Current® Pool Utilizations' should always be between 0% and 100%.