Take the three backup types and time their restores

short · 50 min · Objective 3.2

Task

Build full, incremental and differential backups of the same dataset across a week of simulated changes, then restore from each and time it. The storage and restore-time trade is obvious once you have the numbers and abstract until then.

Steps

  1. Create a dataset of a few hundred megabytes in lab/data/. Take a full backup and record its size and duration in lab/backups.csv.
  2. Simulate six days: each day modify roughly 5% of the files, then take BOTH an incremental (changes since the last backup of any kind) and a differential (changes since the last full).
  3. Record every backup's size and duration. Plot or tabulate how the incremental stays small while the differential grows.
  4. Restore day 6 three ways -- from the full alone where possible, from full plus all incrementals, and from full plus the last differential -- timing each and verifying the restored tree matches with a checksum.
  5. Delete one middle incremental and attempt the incremental restore again. Record what happens, and write the sentence about chain fragility.

Verify

awk -F, 'NR>1 && NF>=3 {n++} END {print n" backup record(s)"}' lab/backups.csv
grep -Eci 'checksum|sha' lab/backups.csv lab/backups.md
grep -Eci 'chain|broken|missing' lab/backups.md
grep -Ec '[0-9]+ ?(s|sec|second)' lab/backups.md

At least thirteen backup records, a restore time for each of the three methods, and the broken-chain result. An incremental restore that still worked with a link missing means the tool is not chaining the way you assumed -- record that, it is a finding.

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