Veritas File System 4.1 Administrator's Guide (HP-UX 11i v3, February 2007)

VxFS Performance: Creating, Mounting, and Tuning File Systems
Choosing mount Command Options
Chapter 2 29
The rename(2) system call flushes the source file to disk to guarantee the persistence of the file data before
renaming it. In both modes, the rename is also guaranteed to be persistent when the system call returns. This
benefits shell scripts and programs that try to update a file atomically by writing the new file contents to a
temporary file and then renaming it on top of the target file.
tmplog
In tmplog mode, the effects of system calls have persistence guarantees that are similar to those in delaylog
mode. In addition, enhanced flushing of delayed extending writes is disabled, which results in better
performance but increases the chances of data being lost or unitialized data appearing in a file that was being
actively written at the time of a system failure. This mode is only recommended for temporary file systems.
Fast file system recovery works with this mode.
NOTE In all logging modes, VxFS is fully POSIX compliant. The effects of the fsync(2) and
fdatasync(2) system calls are guaranteed to be persistent once the calls return. The
persistence guarantees for data or metadata modified by write(2), writev(2), or
pwrite(2) are not affected by the logging mount options. The effects of these system calls
are guaranteed to be persistent only if the O_SYNC, O_DSYNC, VX_DSYNC, or
VX_DIRECT flag, as modified by the convosync= mount option, has been specified for
the file descriptor.
The behavior of NFS servers on a VxFS file system is unaffected by the log and tmplog
mount options, but not delaylog. In all cases except with delaylog, VxFS complies with
the persistency requirements of the NFS v2 and NFS v3 standard.
Unless a UNIX application has been developed specifically for the VxFS file system in log
mode, it will expect the persistence guarantees offered by most other file systems and will
experience improved robustness when used with a VxFS file system mounted in delaylog
mode. Applications that expect better persistence guarantees than that offered by most other
file systems can benefit from the log, mincache=, and closesync mount options.
However, most commercially available applications will work well with the default VxFS
mount options, including the delaylog mode.
logiosize
The logiosize=size option is provided to enhance the performance of storage devices that employ a
read-modify-write feature. If you specify logiosize when you mount a file system, VxFS writes the intent
log in at least size bytes to obtain the maximum performance from such devices. The values for size can
be 1024, 2048, or 4096.