During a software upgrade, a system that has volumes near 128 TB of used physical space will alert you to take certain measures to prevent them from becoming read only.
Compressed volumes near their size limits are monitored at specified thresholds to preserve data integrity. If a volume can be shrunk to fit below the recommended new limit, you will be advised to do so. If volume capacity cannot be reduced to meet the recommended limit, you will be advised to create a non-compressed mirror of the data (if one does not already exist) and delete the primary copy.
Compressed volumes have the following size limits. If a new or existing compressed volume approaches the maximum size, the system issues an alert.
For information about how to move data off a compressed volume, see the Flashes, alerts and bulletins website.