Storage controller providing automatic retention and deletion of synchronous back-up data

A storage controller comprising:

• a processor;
• an internal mass storage device;
• and
• a memory accessible to the processor and having instructions stored therein for configuring the processor to:
• store data in an external mass storage device in response to a first request from a host processing system;
• repeatedly and automatically store in the internal mass storage device a current version of the data as stored in the external mass storage device to internally maintain a plurality of versions of the data, each version associated with a different point in time, in a manner that is transparent to the host processing system;
• receive a second request from the host processing system to modify the data in the external mass storage device;
• and
• modify the data in the external mass storage device in response to the second request while maintaining the state of each of the plurality of versions of the data.

A system comprising:

• a plurality of host processing systems located remotely with respect to each other;
• a plurality of storage controllers located remotely with respect to each other, each of the storage controllers locally coupled to one of the host processing systems and remotely coupled to at least one other of the storage controllers;
• a plurality of mass storage devices located remotely with respect to each other, each of the mass storage devices locally coupled to one of the storage controllers;
• wherein the plurality of storage controllers includes a first storage controller configured to:
• store data in one of the mass storage devices in response to a first request from any of the host processing systems;
• repeatedly and automatically store within the first storage controller a current version of the data as stored in said one of the mass storage devices, in a manner that is transparent to each of the host processing systems, to create a plurality of versions of the data;
• maintain the state of each version within the first storage controller for a duration that overlaps a duration of at least one other version;
• receive a second request from any of the host processing systems to modify the data in said one of the mass storage devices;
• and
• modify the data in said one of the mass storage devices in response to the second request while internally maintaining the state of each of the plurality of versions of the data.

A method of operating a storage controller configured to provide a host processing system with access to a mass storage device, the method comprising:

• receiving data associated with a write request from the host processing system;
• storing the data in the mass storage device in response to the write request;
• receiving a plurality of requests to modify the data from the host processing system over a period of time;
• modifying the data in the mass storage device in response to each of requests;
• and
• at predetermined time intervals during said period of time, automatically storing within the storage controller a copy of the data as currently stored in the mass storage device, to maintain a plurality of time-frozen copies of the data, including maintaining each of the time-frozen copies for a duration that overlaps with that of at least one other of the time-frozen copies.