Wednesday, February 25, 2009

PNUTs, SCADS, Hive

Notes on Tyson's presentation about PNUTS:
  • complaint: not enough control over replication
  • predicate to system, apply to the system before
  • hash or sorted tables
  • no foreign key constraints (not normalized?)
  • selection predicates, and projection from tables
  • no joins
  • per record timeline consistency, all replicas apply updates to record in same order. all updates go to a master, which moves around for performace
  • tyson likes that they took the right pieces out of the db to support the right pieces (read one record at a time)
  • no fine control over replication factor
  • rethink isolation?

Notes on Michael's SCADS talk:
  • Scale independence (borrowed idea from db papers, data independence)
    • No changes to app as you scale
    • latency stays constant
    • const/users stays constant
  • auto scale up/down
  • declarative performance consistency
  • perf. safe query language (cardinality constraints)
  • give developers axis that they understand:
    • performance SLA
    • read consistency (freshness)
    • write consistency
    • durability SLA
    • Session guarantees (monontonic reads, read your own writes)

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