VERITAS File SystemÖ 3.5 (HP OnlineJFS/JFS3.5) AdministratorÆs Guide (December 2002)

Chapter 1

The VERITAS File System

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 17 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.

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. If a system failure occurs, fsck replays any recent

changes to preserve all metadata. Recent file data may be lost unless a request was made to sync it to disk.

Enhanced Performance Mode

VxFS has several mount options that improve performance such as delaylog and qlog.