Veritas™ File System 5.0.1 Administrator's Guide

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 for tmplog, 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 expects the persistence guarantees offered by most other file
systems and experiences 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
work well with the default VxFS mount options, including the delaylog mode.
The logiosize mode
The logiosize=size option enhances 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 the least size bytes or a multiple of size
bytes to obtain the maximum performance from such devices.
See the mount_vxfs(1M) manual page.
The values for size can be 1024, 2048, or 4096.
The nodatainlog mode
Use the nodatainlog mode on systems with disks that do not support bad block
revectoring. Usually, a VxFS file system uses the intent log for synchronous writes.
The inode update and the data are both logged in the transaction, so a synchronous
write only requires one disk write instead of two. When the synchronous write
returns to the application, the file system has told the application that the data
is already written. If a disk error causes the metadata update to fail, then the file
must be marked bad and the entire file is lost.
If a disk supports bad block revectoring, then a failure on the data update is
unlikely, so logging synchronous writes should be allowed. If the disk does not
support bad block revectoring, then a failure is more likely, so the nodatainlog
mode should be used.
A nodatainlog mode file system is approximately 50 percent slower than a
standard mode VxFS file system for synchronous writes. Other operations are
not affected.
37VxFS performance: creating, mounting, and tuning file systems
Mounting a VxFS file system