IBM Storwize V7000 Unified Problem Determination Manual page 329

system uses the same threshold and alerting system and suggests corrective actions
when thresholds are reached. If based on the original, uncompressed capacity that
the system presents to users and applications of the file system.
To free up capacity in a file system, you can either delete files from the file system
or increase the current capacity of the storage pool, which can be used to expand
the volumes that are related to the NSDs from the unused physical capacity. If
corrective action to reduce utilization is not performed before the file system
reaches 100% utilization, the file system goes offline and no longer handles read
and write requests.
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Chapter 8. Troubleshooting compressed file systems