## Backup Methods

Active Backup for Business provides two methods for creating backup chains:

1. Full backup
2. Forever incremental backup

- Full backup:

  A full backup task creates a complete copy of the source data set. Since Synology Active Backup for Business leverages VMware native techniques to perform incremental backup, users whose CBT is disabled or those who do not want to perform incremental backup will have to choose full backup. However, due to the large volume of data to be transferred, full backup is a highly time-consuming process. It also imposes considerable workload on the network each time a backup task is run and may interrupt routine operations of your production site. Besides, continuously arriving full backups will also occupy a great amount of storage in Synology NAS.

- Forever incremental backup:

  There are many different types of incremental backup, such as reverse incremental, forever forward incremental, regular incremental, etc.

  Synology Active Backup for Business uses the the forever-incremental scheme, which is similar to regular incremental backup but only executes a full backup once, rather than periodically. After the initial full backup, the software will only copy increments, which helps save storage space. A forever incremental backup chain is created following the way you can see in the diagram below.

  Other legacy backup solutions can also perform forever-incremental backups but periodically require transforming those increments into full VM backups. Such approaches are time consuming, resource intensive, and require additional storage space. To offset the drawback and to offer the benefit, Synology Active Backup for Business uses forever incremental backup along with exclusive data storage methods based on Synology's unique deduplication technology.

  After a backup task is run, all transferred data will be divided into individual blocks and have a unique reference number. Duplicated blocks will be deleted, while new blocks will be saved in the backup repository. In addition, a recovery point is created with a set of references to data blocks in the repository, which are required to reconstruct the entire VM as of a particular point in time.

  - Here is an example of how it works:

  You run the first full backup of a VM on Sunday. For the sake of simplicity, let’s say the VM consists of only 3 data blocks: A, B, and C.

  So there will be 3 data blocks saved on your Synology NAS.

  Then on Monday, you run an incremental backup, which finds out that block A was deleted, but a new block D was added.

  So the blocks B and C, which remain the same, won’t be saved on your NAS again, while the new block D will. At the end, there will be four blocks on your NAS: A, B, C, and D.

  The Sunday version has a set of references to data blocks A, B, and C, while the Monday version has a set of references to data blocks B, C, and D.

  There will be no need to perform synthetic backup since all recovery points consist of a set of references to data blocks, which helps achieve fast recovery time since the system doesn’t need to process all the increments or run full backup. The benefit of creating a recovery point with referenced blocks along with forever incremental backup is to reduce storage usage and bring fast recovery time. Since this exclusive way of storing data is based on Synology's deduplication technology, please click here to learn more about the built-in feature.