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Bachelor's · Chapter 25 · English

Chapter 25 — Backup and recovery

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Chapter 25 — Backup and recovery

Lesson map

Lesson 25 published. Map, example, EX073.

flowchart TD
  N0["Learning outcomes"]
  N1["25.1 Backup design"]
  N2["25.2 Testing restores"]
  N3["25.3 Recovery objectives"]
  N4["25.4 Recovery plan"]
  N0 --> N1 --> N2 --> N3 --> N4
  N4 --> EX["Worked example"]
  EX --> Q["Exercise EX073"]

Logical drawing

flowchart LR
  N0["Learning outcomes"]
  N1["25.1 Backup design"]
  N2["25.2 Testing restores"]
  N3["25.3 Recovery objectives"]
  N4["25.4 Recovery plan"]
  N0 --> N1 --> N2 --> N3 --> N4 --> Q["EX073"]

[Learning outcomes]
    |
    v
[25.1 Backup design]
    |
    v
[25.2 Testing restores]
    |
    v
[25.3 Recovery objectives]
    |
    v
[25.4 Recovery plan]
    |
    v
[Worked example] --> [Exercise EX073]

Learning outcomes

You will (1) design backups for different threats; (2) test restores; (3) set recovery objectives with business owners.

25.1 Backup design

Backups protect against hardware failure, mistakes and ransomware, but each threat needs different design. Hardware failure needs a copy elsewhere; mistakes need older versions; ransomware needs copies attackers cannot reach or alter. Aisha reviews Ashfield's backups: nightly copies to a storage device in the head office, reachable from the network. She recommends an additional offline or immutable copy, kept away from the head office, so one event cannot destroy everything. The chief executive approves the cost of an additional copy stored with a specialist provider in another town.

25.2 Testing restores

A backup is only useful if it can be restored. Aisha asks when Ashfield last restored a full system from backup. Nobody remembers. She organises a test restore of the shared folders to a separate computer and compares file fingerprints with the originals using hashlib. A few files fail because they were open during backup. She recommends scheduling backups when files are closed and testing restores every quarter. The IT manager adds the quarterly restore test to the calendar and records each result with the number of files checked and verified.

25.3 Recovery objectives

Aisha works with managers to set recovery objectives. For core banking, they accept losing at most fifteen minutes of transactions and need service back within four hours. For shared folders, losing a day is acceptable and recovery within two days is fine. She learns that objectives come from business needs, not technical preferences, and that they decide backup frequency and the recovery methods needed. The managers sign the agreed objectives, and Aisha checks that current backups can meet them. Core banking backups currently run hourly, so she recommends more frequent copies.

25.4 Recovery plan

Aisha writes a recovery plan listing the order of systems to restore, the steps for each and the people responsible. Core banking comes first because members depend on it, followed by email and then shared folders. She notes dependencies: core banking needs the directory service for logins, so that must be restored before it. Dr. Carrow notes that recovery order is often discovered only during a real crisis if not planned. The IT manager walks through the plan with her and adds two missing steps.

Worked example

Aisha adds an offline copy, tests a restore with fingerprints and finds open-file failures, sets objectives with managers and writes a dependency-aware recovery order.

Synthetic case. Backups are synthetic.

Errors and limits

Backups reachable from the network can be destroyed by ransomware.

Exercises

Continue studying — lesson 25 (chapter 25 of 40)

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