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

Chapter 1
The VERITAS File System
Extended mount Options
24
Extended mount Options
The VxFS file system supports extended mount options to specify:
• Enhanced data integrity modes
• Enhanced performance modes
• Temporary file system modes
• Improved synchronous writes
• Large file sizes
See “VxFS Performance: Creating, Mounting, and Tuning File Systems” on page 29 and the mount_vxfs
(1M) manual page for details on the VxFS mount options.
Enhanced Data Integrity Modes
NOTE Performance trade-offs are associated with these mount options.
Most file systems are “buffered” in that resources are allocated to files and data is written asynchronously
to files. In general, the buffering schemes provide better performance without compromising data
integrity.
If a system failure occurs during space allocation for a file, uninitialized data or data from another file
may appear in the extended file after reboot. Data written shortly before the system failure may also be
lost.
Using blkclear Option for 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.
Using closesync Option for 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.
Using the log Option for 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.