After a crash, the system can restore the file-system data structures to
a consistent state by processing the log records, first redoing the operations
for committed transactions and then undoing the operations for transactions
866 Chapter 19 Windows 7
that did not commit successfully before the crash. Periodically (usually every
5 seconds), a checkpoint record is written to the log. The system does not
need log records prior to the checkpoint to recover from a crash. They can be
discarded, so the log file does not grow without bounds. The first time after
system startup that an NTFS volume is accessed, NTFS automatically performs
file-system recovery.