2.7 Durability

Once data is successfully submitted to the system, it is not lost. How? By creating and maintaining multiple copies of data.

Backups

• copy data from a non-volatile storage, such as disk, periodically
• 3 common strategies:
  • Full
    • Easy to implement, easy to restore
    • Takes a long time to backup everything, takes more storage space
  • Differential
    • used with full backus
    • longer restoration time (take detours due to changes)

• • Incremental
    • Same as before, but only backup differences
    • Longer restoration time