Migration of computer data

1. A method for migration of computer data comprising:

modifying a volume boot record of a destination volume on a disk by writing to the volume boot record to place the volume boot record in a first state in which at least a portion of the destination volume becomes inaccessible to a standard file system while maintaining a master boot record of the disk unmodified to enable continued access to the disk using the master boot record;

writing one or more snapshots of a source volume to the inaccessible portion of the destination volume while the volume boot record is in the first state; and

restoring the volume boot record to a second state in which the inaccessible portion of the destination volume becomes accessible to the standard file system.

2. The method of claim 1 , wherein:

the one or more snapshots of the source volume include:

a base snapshot representing a full backup of the source volume; and

one or more incremental snapshots each representing an incremental backup of the source volume; and

at least a portion of one of the one or more incremental snapshots is created after the base snapshot is written to the inaccessible portion of the destination volume.

3. The method of claim 1 , wherein the modifying the volume boot record of the destination volume to place the volume boot record in the first state comprises modifying a signature portion of the volume boot record.

4. The method of claim 1 , wherein the modifying the volume boot record of the destination volume to place the volume boot record in the first state comprises modifying the volume boot record to represent a file structure with a capacity less than an actual capacity of the destination volume.

5. The method of claim 1 , wherein the modifying the volume boot record of the destination volume to place the volume boot record in the first state comprises:

including data indicating a migration state of the method in the volume boot record; and

periodically updating the migration state to indicate a current migration state of the method.

6. The method of claim 1 , wherein the writing the one or more snapshots of the source volume to the inaccessible portion of the destination volume while the volume boot record is in the first state comprises writing the one or more snapshots of the source volume to the destination volume using block accesses while the destination volume is inaccessible to the standard file system.

7. The method of claim 6 , wherein the restoring the volume boot record to the second state comprises restoring at least a portion of the volume boot record to a state indicating that the destination volume is valid using the block accesses.

8. The method of claim 7 , wherein the using the block accesses comprises using private block accesses, public block accesses, or some combination thereof.

9. The method of claim 1 , further comprising preventing the inaccessible portion of the destination volume from undesired changes by supplying a block device filter to prevent public block accesses to the destination volume and to allow private block accesses to the destination volume,

wherein the writing the one or more snapshots of the source volume to the inaccessible portion of the destination volume while the volume boot record is in the first state comprises writing the one or more snapshots of the source volume to the destination volume using the private block accesses while the public block accesses are being prevented.

10. A non-transitory computer-readable medium including computer-executable instructions which, when executed on one or more computers, perform the method as recited in claim 1 .

11. A method for migration of computer data comprising:

creating one or more snapshots including a base snapshot representing a full backup of a source volume and one or more incremental snapshots, including a final incremental snapshot, each representing an incremental backup of the source volume;

modifying a volume boot record of a destination volume on a disk by writing to the volume boot record to place the volume boot record in a first state in which at least a portion of the destination volume becomes inaccessible to a standard file system while maintaining a master boot record of the disk unmodified to enable continued access to the disk using the master boot record;

writing at least a portion of the one or more snapshots to the destination volume after the modifying of the volume boot record and before the creating of the final incremental snapshot;

writing the final snapshot to the destination volume after all of the other of the one or more snapshots have been copied to the destination volume; and

finalizing the destination volume by restoring the volume boot record metadata in the volume boot record to a second state in which the inaccessible portion of the destination volume becomes accessible to the standard file system.

12. The method of claim 11 , wherein the writing at least a portion of the one or more snapshots to the destination volume comprises writing the base snapshot to the destination volume.

13. The method of claim 11 , wherein the modifying the volume boot record of the destination volume to place the volume boot record in the first state comprises zeroing at least a portion of the volume boot record.

14. The method of claim 13 , wherein the modifying the volume boot record of the destination volume to place the volume boot record in the first state further comprises writing metadata indicating a restore state of the method to the volume boot record.

15. The method of claim 14 , further comprising communicating the one or more snapshots from a source computing system to a destination computing system.

16. The method of claim 11 , wherein the destination volume is a volume on a physical disk or a virtual volume represented by a file.

17. A non-transitory computer-readable medium including computer-executable instructions which, when executed on one or more computers, perform the method as recited in claim 11 .

18. A method for migration of computer data comprising:

creating a base snapshot representing a full backup of a source volume;

modifying a volume boot record of a destination volume on a disk by writing to the volume boot record to place the volume boot record in a first state in which at least a portion of the destination volume becomes inaccessible to a standard file system while maintaining a master boot record of the disk unmodified to enable continued access to the disk using the master boot record;

writing the base snapshot to the destination volume;

creating one or more incremental snapshots each representing an incremental backup of the source volume;

writing the one or more incremental snapshots to the destination volume;

preventing modification to the source volume;

creating a final incremental snapshot of the source volume;

writing the final incremental snapshot to the destination volume; and

modifying the volume boot record of the destination volume to a second state in which the inaccessible portion of the destination volume becomes accessible to the standard file system.

19. The method of claim 18 , wherein the preventing modification to the source volume is performed at a user-defined time when it is convenient to have both the destination volume inaccessible to the standard file system as well as the source system unavailable to a second standard file system.

20. A non-transitory computer-readable medium including computer-executable instructions which, when executed on one or more computers, perform the method as recited in claim 18 .