## Storage Reduction

Active Backup for Business provides built-in deduplication technology to greatly enhance data storage efficiency. In addition, full synthetic data storage, which leverages the Btrfs file system, also helps reduce storage usage.

- Built-in deduplication

Data deduplication reduces the size of backup files and is automatically enabled. You can greatly save storage space when backing up several VMs that have a large amount of free space on their logical disks or VMs that have similar data blocks. Data deduplication also works across devices and platforms, so it can delete identical blocks on your PC / server / VM. With this feature enabled, storage efficiency can be significantly enhanced.

Here is an example of how it works:

You execute the first full backup of a VM running Windows Server 2016 from Hypervisor One, and at the same time, you also have a physical server running Windows Server 2016. When you create two backup tasks for these two different devices, only one copy of Windows Server 2016 will be written on Synology NAS since the other will be duplicated almost completely. Even you back up two Windows devices running different operating systems such as Windows 8 and 10, as long as there are identical blocks, they will still be deleted.

There are different deduplication mechanisms in the market. To ensure maximum storage and resource efficiency, Synology Active Backup for Business uses target inline deduplication with hash-based duplicate detection.

Inline deduplication scans the data and deletes the duplicated blocks before it is written to a backup repository. Since this technique clears repetion backup data, it helps to reduce the requirement of storage in a respository. To identify identical blocks, this technique uses cryptographic algorithms such as SHA-256 to calculate a hash for each block, which is the divided fixed length backup data. The blocks with same hashes are considered to be identical and therefore deleted.