HP JFS 3.3 and HP OnLineJFS 3.3 VERITAS File System 3.3 System Administrator's Guide

Chapter 1 27
The VxFS File System
Fast File System Recovery
Fast File System Recovery
The HFS file system relies on full structural verification by the fsck
utility as the only means to recover from a system failure. For large disk
configurations, this utility involves a time consuming process of checking
the entire structure, verifying that the file system is intact, and
correcting any inconsistencies.
VxFS provides recovery only seconds after a system failure by utilizing a
tracking feature called intent logging . This feature records pending
changes to the file system structure in a circular intent log. During
system failure recovery, the VxFS fsck utility performs an intent log
replay, which scans the intent log and nullifies or completes file system
operations that were active when the system failed. The file system can
then be mounted without completing a full structural check of the entire
file system. The intent log recovery feature is not readily apparent to the
user or the system administrator except during a system failure.
Replaying the intent log may not completely recover the damaged file
system structure if the disk suffers a hardware failure; such situations
may require a complete system check using the fsck utility provided
with VxFS.