← VCE Software Development U3O2

Comparing full, incremental and differential backups

They differ in size, time and restore steps: full copies all data, incremental saves changes since the last backup, differential saves changes since the last full backup.

Part of: VCE Software Development - U3O2 - Analysis and Design — Module 80, VCE Data Analytics - U3O2 - Analysis and Design — Module 117, VCE Data Analytics - U4O2 - Cyber Security: Data Security — Module 85, WA Computer Science ATAR Year 11 — Network Communications — Module 142

Understanding Comparing full, incremental and differential backups in VCE Software Development U3O2

What it does: Each differential is measured from the last full backup, so it grows until the next full backup is taken. Each incremental backup holds only changes since the previous backup of any type, so the whole chain must be restored in order. Incremental backups save the least data each night, so they suit tight storage and time limits. The trade-off is a longer restore using several backups.

Common mistakes: An incremental backup copies only the changes since the last backup of any type. Line 2 should say 'changes since Sun', not 'all files copied', which describes a full backup. A full backup copies all the data every time. Copying only changes describes incremental or differential backups.

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This module's key terms are also in a printable crossword (Modules 72–85) and word search (Modules 52–85).

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Learning
Duo
To restore from an incremental backup strategy, which is needed?
The last full backup plus every incremental backup since itThe last full backup plus only the most recent incremental backup
Matches
Restore from incrementals: use only the latest incremental backup, because it holds all the changes
↓
An incremental holds only changes since the previous backup. You must restore the last full backup plus every incremental in order.
Applying
Meanings
Term
full vs incremental vs differential
Meaning
They differ in size, time and restore steps: full copies all data, incremental saves changes since the last backup, differential saves changes since the last full backup.
Practice
IF backupType = "full" THEN
Testing
Gaps
Full: copies selected data every time
Check Answer
Spots
1Sun: FULL backup (all files)
2Mon: INCR (all files copied)

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Quick Questions

1. To restore from an incremental backup strategy, which is needed?
A. The last full backup plus every incremental backup since it ✓
B. The last full backup plus only the most recent incremental backup
Each incremental backup holds only changes since the previous backup of any type, so the whole chain must be restored in order.
2. To restore from a differential backup strategy, which is needed?
A. The last full backup plus every differential backup since it
B. The last full backup plus the latest differential backup ✓
Each differential holds all changes since the last full backup, so the latest one already includes the earlier changes. Only two backups are needed.
3. Which backup type uses the MOST storage space over a week?
A. Full backup, because it copies all data every time ✓
B. Incremental backup, because it copies all data every time
A full backup copies everything each run, so a week of full backups takes the most storage. Incremental backups copy only recent changes.
4. Which backup type is usually the quickest to run each night?
A. Differential, because it saves only changes since the last backup
B. Incremental, because it saves only changes since the last backup ✓
Incremental backups are the smallest and fastest. A differential grows larger each day because it keeps all changes since the last full backup.
5. Which statement about differential backups is correct?
A. They grow larger each day until the next full backup ✓
B. They stay the same small size every day
A differential includes everything changed since the last full backup, so it gets bigger each day until a new full backup resets it.

Match the Pairs

Full backup → Copies all selected data every time. It is the largest and slowest backup, but a restore needs only this one backup.
Incremental backup → Copies only data changed since the last backup of any type. It is the smallest and fastest, but a restore needs the full backup plus every incremental in order.
Differential backup: copies everything changed since the last full backup, so each one grows larger during the week → Mon Full, Tue Diff (Mon changes), Wed Diff (Mon+Tue changes), Thu Diff (Mon-Wed changes)
Restoring after a Thursday crash with a Sunday full backup and daily differentials needs only 2 backups → Restore: Sunday Full + Wednesday Differential
Restore from incrementals: use only the latest incremental backup, because it holds all the changes → An incremental holds only changes since the previous backup. You must restore the last full backup plus every incremental in order.
A small business with limited storage and a short backup window should run a full backup every night → Full backups use the most storage and time. Incremental backups after a weekly full backup suit limited storage and a short window.

Key Term

full vs incremental vs differential
They differ in size, time and restore steps: full copies all data, incremental saves changes since the last backup, differential saves changes since the last full backup.

Fill in the Blanks

1. Full: copies all selected data every time
Hint: Type the word describing how much data a full backup copies each time.
2. Incremental: saves changes since last backup
Hint: Type the word for the point in time an incremental backup compares against (any type of backup counts).
3. Differential: saves changes since last full
Hint: Type the backup type that a differential backup always compares against.
4. Full + latest differential = 2 backups
Hint: Type the number of backups needed to restore when using a full and a differential.
5. Fastest backup, slowest restore: incremental
Hint: Type the backup type that is quickest to make but needs the longest chain of backups to restore.

Spot the Error

Question 1
A Sun: FULL backup (all files)
B Mon: INCR (all files copied)
C Tue: INCR (changes since Mon)
D Restore Tue: Sun + Mon + Tue
Line B — An incremental backup copies only the changes since the last backup of any type. Line 2 should say 'changes since Sun', not 'all files copied', which describes a full backup.
Question 2
A Full backup copies changes only
B Restore needs only 1 backup
C It is the slowest to create
Line A — A full backup copies all the data every time. Copying only changes describes incremental or differential backups.
Question 3
A Differential backup:
B - changes since last backup
C - restore: full + latest diff
Line B — A differential backup copies everything changed since the last FULL backup, not since the last backup of any type. 'Since the last backup' describes an incremental backup.
Question 4
A Sun: full backup
B Mon: differential
C Fri: differential
D Restore: full + all diffs
Line D — Each differential holds all changes since the last full backup. A restore needs only the full backup plus the latest differential (Fri), not every differential.
Question 5
A Storage use per backup:
B Full: largest every time
C Incremental: same size as full
D Differential: grows each day
Line C — Each incremental backup holds only the changes since the previous backup, so it is usually the smallest. It is not the same size as a full backup.

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