System and method for storage unavailability tolerant backup

A method for operating a manager of a backup storage system, comprising:

• initiating, using metadata, a backup generation for a client of clients, wherein initiating the backup generation comprises sending a message to an agent on the client to initiate generation of an incremental backup, wherein the metadata specifies that a backup for the client of the clients is stored on a first storage, wherein the backup storage system comprises the manager, the first storage, and a second storage;
• obtaining the incremental backup from the agent;
• after initiating the backup, making a determination that the first storage is unavailable;
• in response to the determination:
• obtaining an identity of a previous backup from the client, wherein the previous backup is one selected from a group consisting of a full backup and a synthetic backup;
• generating a chain-based backup using the incremental backup and the identity of the previous backup;
• and
• storing the chain-based backup for the client in the second storage of the storages.

A non-transitory computer readable medium comprising computer readable program code, which when executed by a computer processor enables the computer processor to perform a method for operating a manager for a backup storage system, the method comprising:

• initiating, using metadata, a backup generation for a client of clients, wherein initiating the backup generation comprises sending a message to an agent on the client to initiate generation of an incremental backup, wherein the metadata specifies that a backup for the client of the clients is stored on a first storage, wherein the backup storage system comprises the manager, the first storage, and a second storage;
• obtaining the incremental backup from the agent;
• after initiating the backup, making a determination that the first storage is unavailable;
• in response to the determination:
• obtaining an identity of a previous backup from the client, wherein the previous backup is one selected from a group consisting of a full backup and a synthetic backup;
• generating a chain-based backup using the incremental backup and the identity of the previous backup;
• storing the chain-based backup for the client in a second storage of the storages.