Veritas File System 5.1 SP1 Administrator"s Guide (5900-1499, April 2011)

The blkclear option and data integrity
In environments where performance is more important than absolute data
integrity, the preceding situation is not of great concern. However, VxFS supports
environments that emphasize data integrity by providing the mount -o blkclear
option that ensures uninitialized data does not appear in a file.
The closesync option and data integrity
VxFS provides the mount -o mincache=closesync option, which is useful in
desktop environments with users who are likely to shut off the power on machines
without halting them first. In closesync mode, only files that are written during
the system crash or shutdown can lose data. Any changes to a file are flushed to
disk when the file is closed.
The log option and data integrity
File systems are typically asynchronous in that structural changes to the file
system are not immediately written to disk, which provides better performance.
However, recent changes made to a system can be lost if a system failure occurs.
Specifically, attribute changes to files and recently created files may disappear.
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. With this option, the rename(2) system call flushes the source file to
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.
23Introducing Veritas File System
Veritas File System features