Accelerator requires the OptimizedImage attribute

Accelerator requires that the storage has the OptimizedImage attribute enabled.

To ensure that your storage is configured properly, see the documentation for your storage option:

NetBackup Media Server Deduplication Pool.
The OptimizedImage attribute is enabled by default beginning with the NetBackup 7.1 release. If you created the storage servers and pools in an earlier release, you must configure them for OptimizedImage.
See the NetBackup Deduplication Guide.
Backups to a third-party disk appliance.
The storage device must support the OptimizedImage attribute.
See the NetBackup OpenStorage Solutions Guide for Disk.
Cloud storage that NetBackup supports.
See the NetBackup Cloud Administrator's Guide.