The present in invention is directed to a checkpointing filesystem of a distributed-memory
parallel supercomputer comprising a node that accesses user data on the filesystem,
the filesystem comprising an interface that is associated with a disk for storing
the user data. The checkpointing filesystem provides for taking and checkpoint
of the filesystem and rolling back to a previously taken checkpoint, as well as
for writing user data to and deleting user data from the checkpointing filesystem.
The checkpointing filesystem provides a recently written file allocation table
(WFAT) for maintaining information regarding the user data written since a previously
taken checkpoint and a recently deleted file allocation table (DFAT) for maintaining
information regarding user data deleted from since the previously taken checkpoint,
both of which are utilized by the checkpointing filesystem to take a checkpoint
of the filesystem and rollback the filesystem to a previously taken checkpoint,
as well as to write and delete user data from the checkpointing filesystem.
