2.2. Differences between the sparse and dense index

UDS sparse and dense index types differ in memory usage, deduplication window coverage, and physical space requirements, affecting optimal workload selection strategies.

The UDS Sparse Indexing feature relies on the temporal locality of data and attempts to retain only the most relevant index entries in memory. With the sparse index, UDS can maintain a deduplication window that is ten times larger than with the dense index while using the same amount of memory. The sparse index requires ten times more physical space for metadata.

Although the sparse index provides the greatest coverage, the dense index provides more deduplication advice. For most workloads, given the same amount of memory, the difference in deduplication rates between dense and sparse indexes is negligible.