Host computers running applications that store data on a block-based storage system such as a SAN provide hints that differentiate IO data based on which application generated the IO. The hints may include tags that are associated with IO commands sent to the block-based storage system. Each host application is associated with a unique identifier that is placed in the tag. Application name-to-identifier mappings may be sent from the hosts to the block-based storage system. Per-identifier/application deduplication statistics are maintained by the block-based storage system and shared with other block-based storage system. Deduplication is disabled or de-emphasized for IO data generated by applications with statistically low deduplication ratios.