What are three different backup types?

Discussions about backup tend to dive straight into the technical aspects of creating safe copies of vital data. They may miss what is arguably a more important issue, which is the purpose of the backup process itself. When looking at explanations of the different types of backup available to IT managers, it’s worth keeping in mind that backup and restore processes ideally serve business objectives - ensuring business continuity, recovering from disasters like cyberattacks, and enabling operational technology to remain in service with as little interruption as possible.

In reviewing the offerings of the best backup software, we’ve put together options that should keep these higher level objectives in mind, help you create a sound backup strategy, and leverage all the advantages of data backup and recovery.. There are four main approaches to backup: full backup, incremental backup, differential backup, the mirror backup. There is no best type of backup. There is only the method that works best for a particular organization’s needs. That said, the fastest backup and restore process is generally the best, all things considered.

Jump to our Comparison Table for Types of Backup.

Full backups

What is full data backup?

A full backup involves making a copy of an entire digital asset, such as a database or data set. It’s the most basic and rudimentary backup type. Typically, whoever is in charge of backups will conduct a full backup of a file on a periodic basis.

However, its name notwithstanding, in the case of a system backup, a full backup typically does not replicate every single little piece of the system. That is the job of the “Day Zero” backup, which occurs right after a system has been successfully installed and configured. A “Day Zero” backup makes a 100% complete copy of every system file for safe keeping, including files and libraries. These files don’t change very often, so it’s not worth wasting time and resources backing them up as regularly as a full backup process.

Advantage

There’s minimal time needed to restore the data. Since everything is backed up at one time and it’s a copy in its entirety, everything can be restored at one time as well.

Disadvantage

A full backup can take up a lot of storage space and a lot of time to backup. It’s storing and recovering the full data set, which can be quite large, as opposed to storing and recovering the portion of the data set that has changed.

Incremental backups

What is an incremental backup?

An incremental backup copies only that data which has changed since the last full backup and since the last incremental backup. An incremental backup process is particularly useful when dealing with transactional databases, which are constantly changing. When it’s not practical to make a full backup because of resource constraints (i.e. time or storage) or the pace at which data assets change, an incremental approach is more pragmatic.

So, imagine that there is a full backup performed on Sundays. (Weekends are a good time to do an operation with such high network and system load.) On Monday, an incremental backup would only replicate anything that changed in the period between Sunday and Monday. If the incremental backup schedule is daily, then the Tuesday backup would copy any data that changed since Monday, and so forth.

Advantage

Very little storage space is required when executing an incremental backup process since only data that has changed will need to be backed up. It’s also a very fast process given the limited amount of data in comparison to a full backup.

Disadvantage

Restoration is the slowest in comparison. All incremental changes in addition to the full backup need to be reconciled to accurately restore the data, which takes more time than a full or differential backup process. Additionally, if one incremental backup record in the chain is “broken”, it can jeopardize the latter incremental backups.

Differential backups

What is a differential backup?

A differential backup is similar to an incremental backup, with one important difference. Every time a differential process is executed, it backs up all data that has been modified or generated since the last full backup and ignores previous differential backup instances. An incremental backup process only backs up data changes since the last incremental backup was run.

For example, if the full backup was on Sunday, and there is a differential backup done each subsequent day of the week, then Monday’s differential backup will copy data that’s changed since Sunday. The differential backup on Tuesday will copy all the data that’s changed since Sunday, as will the differential backups on Wednesday, Thursday, Friday and Saturday.

Advantage

The recovery process for a differential approach is much faster than an incremental approach since there is only one differential backup block versus the multiple contained in the incremental approach.

Disadvantage

Differential backups require more storage space and more time to backup than an incremental approach.

Mirror backups

A mirror backup is a backup that makes an exact copy of the source data. The advantage of this approach is that it does not store any old or obsolete data. This advantage can cause a problem, though, if files get deleted by accident. Then, they are permanently lost. The mirror backup approach is often used in highly critical systems, such as financial and stock trading platforms where a nearly instant restore of extremely recent data is needed to meet recovery time objectives (RTOs) and recovery point objectives (RPOs).

Backup Types Comparison Table

An alternative to incremental database backups that has a less complicated restore process is a differential backup. Differential backups and recovery are similar to incremental in that these backups grab only files that have been updated since the last normal backup. However, differential backups do not clear the archive bit. So, a file that is updated after a normal backup will be archived every time a differential backup is run until the next normal backup runs and clears the archive bit.

Similar to our last example, if a normal backup runs on Saturday night and a file gets changed on Monday, that file would then be backed up when the differential backup runs Monday night. Since the archive bit will not be cleared, even with no changes, that file will continue to be copied on the Tuesday night differential backup and the Wednesday night differential backup and every additional night until a normal backup runs again capturing all the drive’s files and resetting the archive bit.

A restore of that file, if needed, could be found in the previous night’s tape. In the event of a complete drive failure, one would need to restore the last normal backup and only the latest differential backup. This is less time consuming than an incremental backup restore. However, each night that a differential backup runs, the backup files get larger and the time it takes to run the backup lengthens.

Data loss always sneaks up on you.

One successful breach is all it takes for businesses to lose their fortunes. A recent study found that 29% of businesses that face a data breach end up losing revenue. Among those businesses, 38% experienced a revenue loss of 20% or more.

That’s why businesses back up critical data in order to have a fail-safe, so as to restore systems should a data loss incident occur. Assessing which type of backup fits certain business needs is a smart move, especially since data lives in more places now than ever before.

There are three main backup types used to back up all digital assets:

• Full backup: The most basic and comprehensive backup method, where all data is sent to another location.
• Incremental backup: Backs up all files that have changed since the last backup occurred.
• Differential backup: Backs up only copies of all files that have changed since the last full backup.

Not all IT organizations can support all backup types since network capability may vary from organization to organization. Choosing the right backup method requires a tactical approach — one that can help organizations get the best level of data protection without demanding too much from the network. However, before determining which backup method best suits the needs of your business, you need to understand the ins and outs of the three main backup types mentioned above.

A full backup involves the creation of a complete copy of an organization’s files, folders, SaaS data and hard drives. Essentially, all the data is backed up into a single version and moved to a storage device. It’s the perfect protection against data loss when you factor in recovery speed and simplicity. However, the time and expense required to copy all the data (all the time) may make it an undesirable option for many IT professionals.

Let’s say you have to back up photos from Monday to Friday.

• Monday: You perform a full backup for 100 photos. You get an image file of 100 photos.
• Tuesday: You add another 100 photos and perform a full backup. You get an image file of 200 photos.
• Wednesday: You delete 100 photos and then perform a full backup. You get an image file of 100 photos.
• Thursday: You make no changes to your photos and perform a full backup. You get an image file of 100 photos.
• Friday: You add 200 photos and perform a full backup. You get an image file of 300 photos.

You get five backup files containing 800 photos. Should a data loss incident occur and you need to recover all the photos, simply restore the last version to get all 800 photos.

Here are the advantages and disadvantages of running a full backup method:

• Quick restore time
• Storage management is easy since all the data is stored on a single version
• Easy version control allows you to maintain and restore different versions without breaking a sweat
• File search is easy as it gets

• Demands the most storage space comparatively
• Depending on their size, it takes a long time to back up files
• The need for additional storage space makes it the most expensive backup method
• The risk of data loss is high since all the data is stored in one place

Small businesses that deal consistently with a small amount of data may find full backup a good fit since it won’t eat up their storage space or take too much time to back up.

Incremental backup involves backing up all the files, folders, SaaS data and hard drives that have changed since the last backup activity. This could be the most recent full backup in the chain or the last incremental backup. Only the recent changes (increments) are backed up, consuming less storage space and resulting in a speedy backup. However, the recovery time is longer since more backup files will need to be accessed.

Let’s say you have to back up photos from Monday to Thursday.

• Monday: You add 100 photos and perform a full backup. You get an image file of 100 photos.
• Tuesday: You add another 100 photos (now you have 200 photos) and perform an incremental backup. You get an image file of 100 photos.
• Wednesday: You make no changes and perform an incremental backup. You get an empty image file.
• Thursday: You delete 100 photos and edit the other 100 photos there and perform an incremental backup. You get an image file of only the edited 100 photos.

You get three image files containing 300 photos in total. In case you need to recover all the photos, restore all the image files since the last full backup, including the last full backup and the later incremental backups, to get your 200 photos (including the deleted 100 photos).

Here are the advantages and disadvantages of running an incremental backup method:

• Efficient use of storage space since files are not duplicated in their entirety
• Lightning-fast backups
• Can be run as often as desired, with each increment being an individual recovery point

• Time-consuming restoration since data must be pieced together from multiple backups
• Successful recovery is only possible if all the backup files are damage-proof
• File search is cumbersome – you need to scout more than one backup set to restore a specific file

Businesses that deal with large volumes of data and cannot dedicate time to the backup process will find incremental backup methods effective since they take up less storage space and encourage fast backups. 

Differential backup falls between full backup and incremental backup. It involves backing up files, folders and hard drives that were created or changed since the last full backup (compared to just the changes since the last incremental backup). Only a small volume of data is backed up between the time interval of the last backup and the current one, consuming less storage space and requiring less time and investment.

Let’s say you have to back up photos from Monday to Thursday.

• Monday: You have 200 photos and perform a full backup. You get an image file of 200 photos.
• Tuesday: You add another 200 photos (a total of 400 photos) and perform a differential backup. You get an image file of the newly added 200 photos.
• Wednesday: You make no changes and perform a differential backup on the existing 400 photos. You get an image file of the newly added 200 photos on Tuesday.
• Thursday: You delete 100 photos and edit another 100 photos (total of 300 photos) and perform a differential backup. You get image files of 100 photos, 200 photos and 300 photos.

Recovering 100 photos: Both deletion and editing happen to the added 200 photos. The differential backup will back up the edited 100 photos.

Recovering 200 photos: If you delete 100 photos from the added photos and edit 100 photos from the original photos, the differential backup will back up the edited 100 photos and the 100 added photos (left after deletion).

Recovering 300 photos: The differential backup will back up the edited 100 photos and the added 200 photos.

Here are the advantages and disadvantages of running a differential backup method:

• Takes less space than full backups
• Faster restoration than incremental backups
• Much faster backups than full backups

• Potential for failed recovery if any of the backup sets are incomplete
• Compared to incremental backups, the backup takes longer and requires more storage space
• Compared to full backups, restoration is slow and complex

Small and medium-sized organizations that want to process large volumes of valuable data but cannot perform constant backups will find the differential backup method useful.

Choosing the right backup method depends on your situation. You can determine your situation by asking yourself some primary questions.

• How much data are you backing up?
• How much time can your organization devote to the process?
• How quickly will you need to recover lost data in case of a disaster?
• What operating system(s) and software programs does your business use?

However, the reality is that situations change in the lifecycle of a business and keeping your backup method always in sync with a rapidly changing environment can be tedious. A good, consistent backup strategy is to partner with a robust business continuity and disaster recovery (BCDR) platform that serves every type of backup method for every kind of situation.

This is where Unitrends comes in.

Unitrends employs Incremental Forever to meet aggressive RTOs and RPOs. The first backup is full and all subsequent backups are of the incremental type. It keeps backup windows short and meets tight RPOs. As for meeting RTOs, the Unitrends appliance will create synthetic backups as a passive background operation.

In a nutshell, Unitrends helps organizations build comprehensive backup and recovery systems ensuring uninterrupted operations. Want to learn more? Get in touch with us today!