What is the name of this partition-indexed key-value data structure? Consider a data structure that holds N elements having M partitions each holding N/M elements where M divides N. Each element has a key that satisfies an equivalence relation so as to index into one of the partitions.

Assuming this data structure is implemented within an array insertions are performed by computing the beginning partition location corresponding to the key for the element in question and a linear search is performed until a sentinel empty-value is found (or the end of the partition). Searches are performed analogously.

What is the name of the data structure described above? Does it have any advantage over a hash-table?
Sounds like a hash table to me, with collision resolution by chaining.