Veritas™ File System 5.0.1 Administrator's Guide

disk to guarantee the persistence of the file data before renaming it. The rename()
call is also guaranteed to be persistent when the system call returns. The changes
to file system data and metadata caused by the fsync(2) and fdatasync(2) system
calls are guaranteed to be persistent once the calls return.
Enhanced performance mode
VxFS has a mount option that improves performance: delaylog.
The delaylog option and enhanced performance
The default VxFS logging mode, mount -o delaylog, increases performance by
delaying the logging of some structural changes. However, delaylog does not
provide the equivalent data integrity as the previously described modes 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.
Temporary file system mode
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. VxFS provides the 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
mount -o datainlog option greatly improves the performance of small
synchronous writes.
The mount -o convosync=dsync option improves the performance of applications
that require synchronous data writes but not synchronous inode time updates.
Warning: The use of the -o convosync=dsync option violates POSIX semantics.
Support for large files
With VxFS, you can create, mount, and manage file systems containing large files
(files larger than two gigabytes).
23Introducing Veritas File System
Veritas File System features