Backup system that takes a snapshot of the locations in a mass storage device that has been identified for updating prior to updating

In a computer system comprising a primary system having a mass storage system that stores data blocks in a plurality of storage locations each having a unique address, and a preservation memory means for providing a snapshot storage location, and wherein said computer system further comprises a backup system having a backup storage location, a method of backing up data blocks that are changed during a first time period that runs from first instant in time to second instant in time while reducing the amount of data that must be sent to the backup system, the method comprising the steps of:

• identifying during a first time period that runs from a first instant in time to a second instant in time, only those storage locations of said mass storage system that have changed by virtue of new data stored in them during said first time period;
• preserving a snapshot of the data stored, at said second instant of time, in the identified storage locations so that unchanged data from the identified storage locations is preserved when a write request that writes a new data block into at least one of the identified storage locations is received during a second time period that runs from said second instant of time to a third instant of time, by performing the steps of:
• first checking to determine if the data block stored in said at least one of the identified storage locations at said second instant in time has been preserved in a preservation memory means;
• if the data block stored in said at least one of the identified storage locations at said second instant in time has been preserved in said preservation memory means, then writing said new data block to said at least one of said identified storage locations;
• and
• if the data block stored in said at least one of the identified storage locations at said second instant in time has not been preserved in said preservation memory means, then first writing the data block stored in the at least one of the identified storage locations at said second instant in time into said preservation memory means, and then writing said new data block to said at least one of the identified storage locations;
• and
• transferring the data blocks stored at said second instant of time in the identified storage locations to a backup system.

A method of backing up the mass storage system of computer systems to a backup system, said method comprising the steps of:

• (1) establishing a connection between a backup system having attached backup storage means for storing data blocks and a computer system having attached mass storage means for storing a plurality of data blocks in a plurality of data storage locations, each having a unique address, so that data can be exchanged between said backup system and said computer system;
• (2) said backup system receiving, and said computer system transferring, only those data blocks that have changed during a first time period that runs from a first instant in time and a second instant in time, said transferring and receiving of changed data blocks being performed by executing at least the steps of:
• the computer system identifying storage locations of said mass storage system that have new data stored in them during said first time period;
• during a second time period that runs from the second instant in time to a third instant in time, when a data block that was stored at said second instant in time in any of said identified storage locations is to be changed, the computer system preserving a snapshot of the unchanged data block before said data block is changed so that the unchanged data blocks preserved by said computer system can be retrieved even though new data is written to said mass storage system after said second instant in time,
• the computer system retrieving the data blocks stored, at said second instant in time, in said identified storage locations and transferring the retrieved data blocks to said backup system;
• and
• the backup system receiving the transferred data blocks;
• and
• (3) repeating steps (1) and (2) for each of said plurality of computer systems so that each of said plurality of computer systems has transferred, to said backup system, the data blocks that have changed during said first time period.

A computer-readable medium for use in a computer system comprising a mass storage means that stores a plurality of data blocks in a plurality of storage locations, each having a unique address, said computer-readable medium having computer-executable instructions comprising:

• means for identifying which of said storage locations has had new data blocks stored therein during a time period that runs from a first instant in time and a second instant in time;
• means for preserving a static snapshot, at said second instant in time, of the storage locations that have had new data blocks stored therein between said first instant in time and said second instant in time, said static snapshot including at least one unchanged data block that has been transferred, after said second instant in time, from one of said identified storage locations to said means for preserving a static snapshot before said one of said identified storage locations is changed by having a new data block written thereto;
• means for retrieving the data blocks that were preserved by said static snapshot;
• and
• means for transferring the retrieved data blocks to a backup system.