A data backup system for use with a server running a storage application that
writes
and reads data blocks. The system includes a self archiving log structured volume
for copying blocks from an active volume while the application is running without
contending with the application for access to data blocks. The volume records the
result of every write event in a new location in primary storage, forming a chronological
log of the state changes the volume undergoes. The volume records in the log the
points in time (synch events) when the blocks of the volume are in a consistent
state with respect to the application. The system further includes backing storage
to store the archived blocks and synch events of the volume. The volume migrates
inactive segments of its log to the backing storage and ensures that a volume can
be reconstructed from a fixed number of log segments.
