Prefetcher

Prefetcher promotes the BLOBs in Hermes to improve the I/O performance. It predicts the next BLOBs to get and place them in a queue.

Algorithms

Size: Determine the size of a BLOB. For example, smaller size BLOB will require the fewer number of target buffers and can be prefetched with higher precedence.
Frequency: Count the number of times a BLOB has been read since its creation.
Recency: Calculate the interval between the present and the last access time of a BLOB.