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A mixed, or heterogeneous, cluster is one that comprises two or more different types or node. For compression, there are two main concepts in play in a mixed cluster:
The former happens in L1 memory and not on-disk. As such, only F910, F900, F810, F600, F200, F700/7000, H5600, and A300/3000 storage pools may contain compressed data.
In general, OneFS does not allow deduplication across different disk pool policies. For inline deduplication, a deduplicated file that is moved to another tier will retain the shadow references to the shadow store on the original disk pool. While this behavior violates the rule for deduping across different disk pool policies, it is preferred to do this than rehydrate files that are moved. Further deduplication activity on that file will no longer be allowed to reference any blocks in the original shadow store. The file will need to be deduplicated against other files in its new node pool.