Differential and Incremental backups: Why should you care?

Differential and Incremental Backup DiagramDifferential and Incremental  backups are called “Intelligent” backups. Because only a small percentage of information on a computer changes on a daily basis, running a full-sized backup every day can result in wasted time and disk space. Differential and Incremental backups allow you to backup only these changes in different ways; saving time, space and money. Keep reading to learn more about Differential and Incremental backups and why you should care about them.

Editor’s Note: Most backup companies recommend a full backup weekly as part of an overall backup/data-integrity plan. Additionally, Full backups are recommended if there are major changes to a system (e.g. a change in Operating Systems, an update in software or new software installation).

Differential backups: Differential backups are based on the last full backup performed and backup all changes since the last Full backup was performed.

Incremental backups: Incremental backups are based on the last backup performed and backup only the changes since that last backup (Full or Differential).

Incremental and Differential backups were both designed to allow you to backup only files that have changed, although they differ on which files are selected. Incremental backups will back up any changes you have made since your last backup (regardless of type), whereas Differential backs up all of the changes since your last Full backup.

As part of your overall backup strategy, the option to select an Incremental backup a or Differential backup can help manage your data storage and backup job speed. For more detailed information relating to how Differential or Incremental backups differ, please see our FAQ: The differences between a Full, Incremental, or Differential backup

Selecting the Right Backup Policy

Choosing the right setup for your backup policy will depend on your space, time, and the level of data protection desired. For more information on PC backup, view post on understanding your PC backup software needs.

 

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13 Comments:

  1. BASED ON READING YOUR ARTICLE, PLEASE VERIFY THESE STATEMENTS ARE VALID:

    1) An incremental backup can result in many, many files and after the
    next full backup is performed [or a restore takes place] these
    incremental files are useless and may be safely deleted.
    2) A differential backup always consists of TWO files:
    a) the full backup
    and b) a differential file [containing whatever has changed since the
    full backup]

    Prior to creating a new differential file it is safe to delete the latest differential file since it will be replaced by the new one. When a restore is performed only the full backup and the one [and only] differential file will be used.

    • Hi Dan, I have tried to answer all of your questions but please let me know if you need any further clarification. I hope this helps.

      1) An incremental backup can result in many, many files and after the next full backup is performed [or a restore takes place] these incremental files are useless and may be safely deleted.

      Incremental backups are, yes, only portions of file backups. After a full backup has been triggered – all files that were selected will be backed up and so long as you are comfortable with losing “versions” of the previous files, you are free to remove the other incremental backups.

      2) A differential backup always consists of TWO files:
      a) the full backup
      b) a differential file [containing whatever has changed since the full backup]

      Our differential backups still build files (you should be using the “Append” mode). They will be something like “NovaBACKUP_20140821140000.nbd”. Each differential file created will contain the most recent version of any file that has changed since your last full backup.

      3) Prior to creating a new differential file is it safe to delete the latest differential file since it will be replaced by the new one? When a restore is performed, will only the full backup and the one [and only] differential file will be used?

      Deleting differentials like this does remove versions. For example, if you have File X that is modified on Monday, Tuesday, Wednesday and Thursday and assuming your full backup happens on Sunday – the differential you create on Monday will contain Monday’s change, the file created on Tuesday will contain Tuesday’s change, etc. The file created on Tuesday, for example, will not have BOTH Monday and Tuesday’s version, it will have ONLY Tuesday’s version. This is why I don’t necessarily recommending deleting things like that until you are absolutely sure you don’t want the versions they contain.

  2. I had run a full backup. A week later I thought I would try a differential thinking it would be short and quick. After letting it run for an hour or so and seeing that it was only 5% complete it sure seemed to me that something was wrong. Shouldn’t incrementals and differentials run fairly quick?

    • Differential backups have to check to see what changed since your last full backup. It then only backs up those changes. Incremental backups are based on the last backup performed and backup only the changes since that last backup (Full or Differential). Because only a small percentage of information on a computer changes on a daily basis, running a full-sized backup every day can result in wasted time and disk space. I would try to run full backups once a week and differential backups daily. I imagine a lot changed in the week period from the time your ran your full backup to the time you decided to run a differential. If you had run another full backup, then scheduled your differential to run the next day, it would be much faster. I hope this helps.

  3. While installing nova backup, if i select full backup on first the size come 14GB e.g. then after amending the backup to differential the same file size decreased to 930mb only.
    let me know where i am doing the mistake.
    Regards,

  4. Thanks for finally talking about >Differential vs. Incremental Backup:
    Why you should care | NovaStor <Loved it!

    • Crooken teeth,

      I might have this backward, but I think the answer to your question is as follows.

      With both of these you have to take a full backup initially so there’s no difference there. However after that the main difference is the size of the backup and the retention.

      Incremental: If you lose any incremental then you can never really claim to have a full backup of all the points in time.
      Differential: Since each backup is recording the changes from the full, this backup will be larger and larger as time goes on, but you will not have to keep a long string of incrementals to keep track of.

      In the end, it depends on what media you are backing up to and how long you are willing to take to do a restore.

      Incementals are great for small daily backups. They are quick and don’t take up much space. A differential backup will take longer and longer and the only way to make it faster is to reset to a new full backup. However, you can do a complete restore with a single differential when it would take multiple incremental restores to arrive at the same point in time restore.

      Clear as muddy water? Hope I’m accurate and it answered your question.

  5. Hello, great reading and nice break down of differential and incremental. I am presently testing version 18.5, build 926 running on Windows Pro 64bit. The app does not allow me to generate a differential backup after generating the weekly backup and retention schedule. This means the acceptance testing of the NovaStor app is unsuccessful. Do you have a bug in V18.5/926 ? Or, is it time for me to start acceptance testing a different solution ? Thank you for reading.

    • Hi Lindsey, Can you provide a little more information here. I’m not familiar with what you mean by Windows Pro 64bit. Since I have never heard of that Operating System I don’t know exactly how to answer your question. Please reply back with the actual Operating System taken from the Control Panel -> System area of Windows.

  6. Great information for someone new to the techniques used for backing up a system. I like the quick comparison for easy reference.

  7. I had a issue where a customer deleted all his documents in the Windows user/documents folder. I was doing a full backup nightly, thus when the full backup ran after he deleted all his documents it wrote over the user\documents on the previous nights backup with an empty user\documents folder. What Novastor backup scenario could I have used to have prevented this?

    • If you would have utilized Write Mode “Append” instead of Write Mode “Overwrite” it would have allowed storing more than one full backup. This option is in the Job Settings screen, while editing a backup job in the “Backup” tab. It is also a setting that can be changed when creating a new Image Backup Schedule job, when creating a scheduled image backup job, the option/choice will be listed as “Overwrite previous image backup”. You can simply un-check that box to not use overwrite so that a separate image backup is created each time the job runs. For purposes of file backup this is detailed in the two written guides that we have on the subject and one video guide:

      Written Articles:
      Create a weekly full backup, a daily differential backup, and a monthly image backup with retention
      This step-by-step guide will walk you through how to create, schedule, and implement a backup retention policy for a weekly full backup, a daily differential backup, and a monthly full image backup. This is the recommended way to backup all of your data while making sure that you don’t run out of space over time.

      Backup with Retention Walkthrough
      This step-by-step guide will walk you through setting up a scheduled file backup job in NovaBACKUP combined with configuring a data retention policy so that you don’t run out of space over time. This guide does not cover creating a scheduled image backup job, for a guide that covers that click here.

      Videos:

      Complete Backup and Creating a Backup Schedule
      This step-by-step how-to video shows one of NovaStor’s customer support technicians setting up a complete backup plan for a customer.

      Backup With Retention Walkthrough (Video)
      This step-by-step how-to video will walk you through setting up a scheduled file backup job in NovaBACKUP while utilizing data retention so that you don’t run out of space over time.

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