Unitrends uses backups to create recovery points for your data. Backups are run in different modes and are organized into backup groups. Your backup strategies determine which modes you will use.
Unitrends backups fall into two general categories: local backups and backup copies. Local backups are stored on the appliance. These backups are immediately accessible and enable you to meet low RTOs. Backup copies are stored on an offsite target. These backups are duplicates (hence, "copies") of your local backups, and are used for long-term retention and disaster recovery.
Backup modes determine what data to include in the backup. These modes protect all types of data and apply to asset-level backups, host-level backups, and application backups.
While Unitrends supports a variety of backup modes that give you flexibility in protecting your assets, not all backup modes are supported for all assets. When creating a backup job for a given asset, only supported modes are available for selection.
While creating backup jobs, you can select these backup modes: full, incremental, differential, and selective. In addition to these, the appliance automatically creates synthetic backups as needed. See the following for a description of each:
A full backup captures all data on the asset:
• | For asset-level backups run with a Unitrends agent, this includes all file system and operating system data required to restore the asset. You can specify data to include or exclude from the full backup. |
• | For host-level backups, this includes VM metadata (configuration files) and blocks of all disks attached to the VM. For VMware, you can specify disks to exclude from the full backup. |
• | For application backups, all data is included in a full backup. |
• | A successful full backup must exist before a differential or incremental can run. |
An incremental captures changes in the protected data since the last successful backup (of any mode). Therefore, incremental backups are smaller and can run more quickly than full backups, but they depend on the previous backups.
The diagram below illustrates incremental backups for an asset. In this example, the incremental runs once a day, but you can schedule them more frequently if desired.
A differential captures changes in the protected data since the last successful full backup. The diagram below illustrates differential backups for an asset. Each differential captures all changes in the protected data since the full backup on Day 1. For example, the differential on Day 4 captures all changes since the full backup on Day 1, including the changes that were already captured by the differentials on Day 2 and Day 3.
A selective backup is run independently of any full, differential, or incremental backup and captures only the data that you have selected. Selective backups can be used only for asset-level backups.
A synthetic backup is a full or differential backup that the Unitrends appliance synthesizes by superimposing the incremental backups on the last successful full backup. It then uses the synthesized backups to create recovery points for quick recovery. Synthetics are also used for backup copy jobs as incrementals cannot be copied directly.
The Unitrends appliance uses the following factors to determine when to create a synthetic backup:
• | Amount of data being protected on the appliance |
• | Number of days from the last full backup |
• | Number of incremental backups since the last full backup |
• | Load on the appliance |
Synthetic backups are created only for asset-level backups and host-level backups of VMware and Hyper-V VMs. Synthetic backups are appliance-side only and do not impact the assets or networks. The diagram below illustrates a synthetic backup. For more information, see KB 3560.
To protect your data, you will likely use a combination of backup modes. Your Unitrends appliance organizes an asset's backups into groups to manage any interdependencies between backups. The appliance creates a new group when it runs or synthesizes a full backup. Each subsequent differential or incremental forms a link in the chain of backups that constitute the group. Each link in the chain is necessary for data recovery.
The following diagrams illustrate backup groups:
The diagram below illustrates the incremental forever backup strategy for an asset. The strategy begins by automatically promoting the first scheduled incremental to a full backup. Thereafter, incremental backups run at the times specified in the job schedule. When the appliance determines a new full backup is necessary, it synthesizes a full backup and starts a new backup group.
The diagram below shows two backup groups containing full, differential, and incremental backups.
Note: Selective backups are supported only for asset-level protection.
Selective backups exist independently of backup groups. The diagram below illustrates a backup group and selective backups for one asset. Both a selective backup and an incremental backup ran on Day 3. On Day 5, a differential backup and a selective backup ran. However, only the incremental and the differential belong to the group associated with the full backup run on Day 1.
A data protection strategy consists of utilizing one or more of the backup modes described above. Your strategy is implemented when you schedule jobs to occur at intervals and times you specify. For example, the incremental forever strategy consists of the full and incremental backup modes.
Unitrends recommends using the incremental forever backup strategy when possible, where an initial full backup is followed by incrementals at the frequency and times required to meet your RPOs.
In some cases, you will want to use a different backup strategy (such as weekly fulls with incremental or differentials). You can customize your backups to fit any strategy, using the backup modes as desired. Examples of cases when you would not use the incremental forever strategy include:
• | Protecting assets for which incrementals are not supported (such as Exchange and SharePoint applications, VMware hardware version 4 VMs, and VMware templates). |
• | Needing to control when full backups are run. (In most cases, this is not an issue since synthetics are run locally on the appliance and do not impact network or asset performance. But you may choose to schedule weekly fulls if appliance resources are taxed at certain times of the day or week.) |