Resilience concepts

High Availability (HA) 🏷️¶

TL;DR

• Goal: Maximizing a system's uptime 📈.
• User disruption is acceptable ✅.
• More budget friendly 🏷️
• With Spare infrastructure ready to switch to you can minimize outages 👌.
• cope through disaster.
• e.g. 4x4 repearing a tire hole with a spare tire
  • spare tire.
  • some user disruption while doing so.

Fault-Tolerance (FT) 💰¶

^6c176e

• Goal:
  • Work through failure of some its components 🩹
  • ****minimize outages**** ⚡.
• User disruption not allowed or acceptable 🚫.
• More expensive 💸.
• Outages must be minimized and the system needs levels of redundancy.
• Mission or life critical situations 🔫
• operate through disaster.
• e.g. Resilient systems on large planes
  • (like extra engines than it needs to so it can operate through failure)

Disaster Recovery (DR) ☠️¶

• what to plan for ? and do when disaster occurs ?
• *e.g.* DR Process are pilot or passanger ejection systems.
• Goal: DR is a process designed to keep the non replaceable parts safe.
• Set of policies, tools and procedures to enable the recovery or continuation of vital technology infrastructure and systems following a natural 🍃 or human-induced disaster 🤡.
• DR can largely be automated to eliminate the time for recovery and errors.

This involves:

• Pre-planning
  • Ensure plans are in place for extra hardware
  • [DO NOT STORE] backups at the same site as the system.
• DR Processes
  • Cloud machines ready when needed.
  • Run periodic DR Testing.
  • all the process and tools should be properly documented.
    • all the parties involved should run periodic DR Testing from time to time to minimize human error.
    • all logins to key systems need to be available for staff at time of disaster.
• This is designed to keep the crucial and non replaceable parts of the system in place.
• Used when HA and FT don't work.