Local Storage ~ Storage Engine

Operations

• Put(k, v)
• Get(k)
• Delete(k)
• ScanRange(from, to)

Guarantees

• ACID
  • Atomicity
  • Consistency
  • Isolation
  • Durability

Hardware

• HDD
  • big and cheap
  • mechanical!
  • move arm
  • read sectors
  • 6ms for one rotation
  • do not shout at them

• SSD
  • small and expensive
  • flash memory
  • cell -> page -> block
  • garbage collection

• Require sequential reads and writes!

Impl

• B-Tree
• B+ -Tree
• log-structured-merge-tree

Keys in memory, values on disk!

Write-Ahead logging! -> Durability