3. Data Protection and Recovery
Outcome
Section titled “Outcome”Separate availability, durability and recoverability, then choose protection mechanisms using failure domains, recovery point and recovery time.
Level: Foundation · Time: 45 minutes · Prerequisite: Storage Building Blocks
| Mechanism | Primary purpose | Does not replace |
|---|---|---|
| RAID/mirroring | remain available through selected device failures | independent backup |
| Snapshot | preserve a point-in-time logical version | isolated off-system copy |
| Replication | maintain another copy, synchronously or asynchronously | versioned recovery from every corruption/operator error |
| Erasure coding | tolerate fragment loss with efficient capacity | correct placement and repair operations |
| Backup | recover independent historical copies | continuously available primary storage |
RPO bounds acceptable data loss in time. RTO bounds acceptable restoration time. Neither is proven by configuration alone; recovery must be tested.
Practice
Section titled “Practice”Use the Universal RAID Planner to compare RAID 6, RAID 10 and RAID-Z2. Then use the Erasure Coding Lab to fail fragments at and beyond tolerance.
Check your understanding
Section titled “Check your understanding”- Why is a snapshot on the same failed array not an independent backup?
- What can make a mathematically recoverable erasure-code layout operationally unsafe?
- When might RAID 10 be preferred over a parity layout despite lower usable capacity?
Production boundary
Section titled “Production boundary”Capacity formulas do not predict rebuild time, correlated failure, latent corruption or workload impact. Validate vendor implementation and measured recovery behavior.
Next step
Section titled “Next step”Continue to SAN Architecture.