Red Hat GLOBAL FILE SYSTEM 5.2 Guida di Installazione Scaricare il pdf (Pagina 44)

Each file inode and directory inode has three time stamps associated with it:

• ctime — The last time the inode status was changed

• mtime — The last time the file (or directory) data was modified

• atime — The last time the file (or directory) data was accessed

If atime updates are enabled as they are by default on GFS and other Linux file systems then

every time a file is read, its inode needs to be updated.

Because few applications use the information provided by atime, those updates can require a

significant amount of unnecessary write traffic and file-locking traffic. That traffic can degrade

performance; therefore, it may be preferable to turn off atime updates.

Two methods of reducing the effects of atime updating are available:

• Mount with noatime

• Tune GFS atime quantum

10.1. Mount with noatime

A standard Linux mount option, noatime, can be specified when the file system is mounted,

which disables atime updates on that file system.

Usage

mount BlockDevice MountPoint -o noatime

BlockDevice

Specifies the block device where the GFS file system resides.

MountPoint

Specifies the directory where the GFS file system should be mounted.

Example

In this example, the GFS file system resides on the /dev/vg01/lvol0 and is mounted on

directory /gfs with atime updates turned off.

mount /dev/vg01/lvol0 /gfs -o noatime

Chapter 3. Managing GFS

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Red Hat GLOBAL FILE SYSTEM 5.2 Guida di Installazione Pagina 44