Skip to content

WA5. Differential vs. Incremental Backups

Statement

  • In unit five, we are introduced to data backup and recovery concepts.
  • For your written assignment:
    • Discuss the differences between conducting differential and incremental backups with emphasis on:
      • Database backups
      • Restore and reliability
      • Do they always work?

Solution

Introduction

  • There are three main types of backups: Full, incremental, and differential. Each of them has its pros and cons. The text will discuss each type in detail.
  • The first type is special; the full backup includes all files, filegroups, and transaction logs in the database (Microsoft, 2022, Backup Overview).
  • The other two types (incremental and differential) rely on the full backup; there must be a full back prior to the incremental or differential backup (Fellows & Crocetti, 2022).
  • The type of backup that an organization needs depends on multiple factors; rarely, a single type of backup is enough. The DBA usually combines two or more backup types into a backup scheduled strategy that ensures data safety at all times.
  • The 3-2-1 rule is an example of a good backup strategy; in fact, it is considered a best practice; the rule states that the DBA should have three copies of the backup, on two different media, and at least one of them is offsite (Castagna, n.d).

Full Backup

  • A full backup is a backup of the entire database; it includes all data (files and file groups) along with all transaction logs that are necessary for the restoring process (Microsoft, 2022, Backup Overview).
  • Usually, the transactions log contains changes or transactions that have not been committed yet (during the time of failure or the backup/recovery process).
  • A full backup is the most reliable, secure type of backup if scheduled properly (following a method like the 3-2-1 rule); however, it is also the most expensive, time-consuming, and resource-intensive type of backup.

Differential Backup

  • A Differential backup is a backup of the changes that have occurred since the last full backup, so this must have a prior full backup called the base deferential (Microsoft, 2022, Backup Overview).
  • A differential backup size will be smaller than a full backup, but it will increase as the time between the full backup and the differential backup increases.
  • A differential backup of data after 5 days will be larger than a differential backup of data after 1 day, the first will include all the changes that occurred during the 5 days, while the second will include only the changes that occurred in 1 day.
  • The regularly run differential backups are optimal for time consumed; since they only include changes for small periods, and suit all-day busy applications.
  • In terms of recovery, the latest differential backup must be added to the latest full backup to restore the database to the latest state (Microsoft, 2022, Backup Overview).

Incremental Backup

  • An incremental backup is a backup of the changes that have occurred since the last backup, regardless of the type of backup (Microsoft, 2022, Backup Overview).
  • An incremental backup size will be the smallest of the three types discussed in this text; since it will always include the changes that happen on the last day. Since the size is small, the time consumed in backing up is also the smallest.
  • Although the individual incremental backup size is very small, Fellow and Crocetti (2022) showed the combined size of all incremental backups throughout a period is almost identical to the size of a differential backup.
  • In terms of recovery, all individual incremental backups must be added to the latest full backup to restore the database to the latest state; this means that incremental backups take more time to restore than differential backups (Microsoft, 2022, Backup Overview).

Differential vs. Incremental Backups

  • As we saw earlier, the incremental backup has a smaller size and time consuming than the differential backup, but it may have a longer recovery time than the differential backup.
  • Also, the fact that the individual incremental backup only holds data changes for one day means that each individual incremental backup must be stored on a separate media device (Fellows & Crocetti, 2022).
  • Both backup types start from a full backup, and if both types run by the same rate after the full backup (say every day), the size of both backups will be identical on the first day, then the incremental backup will be smaller than the differential backup on the second day, and so on.

Summary and Conclusion

  • As we saw in this text, a combination of backup types is the best way to ensure data safety;
  • A weekly schedule, with full backup on the first day, then differential backup for the rest of the week, is a good example of a backup strategy.

  • We are now able to answer the questions of the assignment:

  • Discuss the differences between conducting differential and incremental backups with Restore and reliability:

    • The differential backup is more available and reliable than the incremental backup.
  • Do they always work?
    • No, both of them require a full backup to be available for the restore process.

References