VERITAS File System 3.5 (HP OnlineJFS/JFS 3.5) Administrator's Guide (August 2003)

Chapter 1
The VERITAS File System
Extended mount Options
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The mount -o log intent logging option guarantees that all structural changes to the file system are logged
to disk before the system call returns to the application. If a system failure occurs, fsck replays any recent
changes to preserve all metadata. Recent file data may be lost unless a request was made to sync it to disk.
Enhanced Performance Mode
VxFS has several mount options that improve performance such as delaylog and qlog.
Using the delaylog Option for Enhanced Performance
The default VxFS logging mode, mount -o delaylog, increases performance by delaying the logging of
some structural changes, but does not provide the equivalent data integrity as the previously described
modes. That is because recent changes may be lost during a system failure. This option provides at least
the same level of data accuracy that traditional UNIX file systems provide for system failures, along with
fast file system recovery. delaylog is the default mount option.
Temporary File System Modes
On most UNIX systems, temporary file system directories (such as /tmp and /usr/tmp) often hold files that
do not need to be retained when the system reboots. The underlying file system does not need to maintain
a high degree of structural integrity for these temporary directories.
Using the tmplog option For Temporary File Systems
VxFS provides a mount -o tmplog option which allows the user to achieve higher performance on
temporary file systems by delaying the logging of most operations.
Improved Synchronous Writes
VxFS provides superior performance for synchronous write applications. The default mount datainlog
option greatly improves the performance of small synchronous writes.
The mount convosync=dsync option improves the performance of applications that require synchronous
data writes but not synchronous inode time updates.
CAUTION The use of the convosync=dsync option violates POSIX semantics.
Support for Large Files
VxFS can support files up to two terabytes in size. See
“largefiles | nolargefiles” on page 35 for information
on how to create, mount, and manage file systems containing large files.
CAUTION Some applications and utilities may not work on large files.