Differentiated Storage Services

Intel Labs
SOSP 2011

Key Idea:
1. Classify I/O requests. Classifiers preserved across different layers: applications, file systems, and block storage systems.
2. Division of labor for I/O performance optimization:
     File systems or Applications: develop classification schemes based on its own semantics (how to classify, policy for each class)
     Operating Systems: Preserve classifiers when passing/translating I/O requests.
     Block Storage System: Implementing the polices using its internal mechanisms.

Example:
    File System classify based on block types, and assign priorities to each block class
    Storage systems implement priority policies by giving cache preference to higher priority blocks (thus no priority reversion)

Comparison of DSS and IOFlow:
     1. IOFlows give differential treatment to VM level I/O flows, while DSS give differential treatment to each I/O request. (Different Granularity)