This feature is new in the Solaris Express 4/04 release and in the Solaris 9 9/04 release.
Logging is now enabled by default for all UFS file systems except under the following conditions:
When logging is explicitly disabled
If insufficient file system space exists for the log
In previous Solaris releases, you had to enable UFS logging manually.
UFS logging packages into one transaction the multiple metadata changes that compose a complete UFS operation. Sets of transactions are recorded in an on-disk log, and then applied to the actual UFS file system's metadata.
UFS logging provides two advantages:
If the file system is already consistent because of the transaction log, you might not have to run the fsck command after a system crash or an unclean shutdown.
Starting in the Solaris 9 12/02 release, the performance of UFS logging improves or exceeds the level of performance of nonlogging file systems. This improvement can occur because a file system with logging enabled converts multiple updates to the same data into single updates. This capability reduces the number of overhead disk operations that are required.
For more information, see “What’s New in File Systems in the Solaris 10 Release?” in the System Administration Guide: Devices and File Systems. See also the mount_ufs(1M) man page.