Legacy Backup Format

The legacy backup format is a proprietary simple backup format for storing backup data on backup storage of any type.

As of Backup for Windows version 7.0, the legacy backup format is supported along with the new backup format.

The legacy backup format supports the following backup types:

• File backup
• Image-Based Backup
• VMware Backup
• Hyper-V Backup
• Microsoft SQL Backup
• Microsoft Exchange Backup

The legacy backup format has two modes:

• Simple Mode
• Advanced Mode

Support for Major Storage Providers

The legacy backup format is supported by major storage providers. Refer to the list of supported features for providers in the Feature Comparison chapter.

Simple Mode

This is a basic backup mode that stores files in backup storage as is. The simple mode supports only file-level backup. No file versions are supported. This mode suits users who aim to have a similar file and folder structure to their backup source in backup storage.

Advanced Mode

Advanced mode supports the following features:

• Compression
• Encryption
• Versioning
• Block-Level backup type
• Retention Policy

Compression

For backup data compression, a standard Gzip mechanism is used.

Encryption

For encryption, MSP360 backup uses the Advanced Encryption Standard specification. Different key lengths are supported as well.

Versioning

The advanced mode supports backup data versioning. Each time a backup is made, backup content is compared with the previous one and if there is a difference, a new version is uploaded. Object version management is done via the retention policy.

Block-Level Backup Type

Block-level is a backup approach where instead of a full copy backup (full backup) to backup storage, a backup sequence of a first full backup and following incremental backups is established. A backup source is divided into blocks, and only modified blocks are uploaded to backup storage.

The modification date is the criterion for deciding whether a file or folder should be backed up. If a file was modified after the last backup time, it is divided into blocks, then the blocks are compared. Modified blocks are uploaded to backup storage.

Block size varies for different kinds of backup sources. For a file-level backup, the block size depends on the file size:

• The block size equals 128 kB if the file size is less than 512 GB.
• The block size equals 256 kB if the file size is less than 1024 GB.
• The block size equals 512 kB if the file size exceeds 1024 GB.

For image-based, Microsoft Exchange, and VMware backups, the block size is 1 MB.

You can always run a full backup as well to be able to purge outdated file versions according to the regular retention policy settings. The backup service cannot delete a previous file version unless a newer full backup is uploaded to the storage, because this version is used for restoring the file.

Retention Policy

Multiple version support allows you to set up a flexible retention policy for backups.

Thus, you can make the backup service delete file versions that were modified or uploaded to your backup storage more than a certain number of days ago. Once this retention policy option is enabled, you can also keep the last version of each file regardless of when it was backed up. Also, the user can specify the maximum number of versions. According to these settings, the specified number of file versions is kept on backup storage. Along with version settings, you can specify a time period for which locally deleted files should be kept in the backup storage before purging.