Red Hat GFS 6.1 -, Administrator'S Manual

Page: 65 / 86

Chapter 5. Managing GFS 51
5.9.1.1. Usage
mount
-t gfs
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.
5.9.1.2. Example
In this example, the GFS file system resides on the
/dev/vg01/lvol0
and is mounted on
directory
/gfs1
with atime updates turned off.
mount -t gfs /dev/vg01/lvol0 /gfs1 -o noatime
5.9.2. Tune GFS
atime
Quantum
When
atime
updates are enabled, GFS (by default) only updates them once an hour. The
time quantum is a tunable parameter that can be adjusted using the
gfs_tool
command.
Each GFS node updates the access time based on the difference between its system time
and the time recorded in the inode. It is required that system clocks of all GFS nodes in a
cluster be synchronized. If a node’s system time is out of synchronization by a significant
fraction of the tunable parameter,
atime_quantum
, then
atime
updates are written more
frequently. Increasing the frequency of
atime
updates may cause performance degradation
in clusters with heavy work loads.
By using the
gettune
flag of the
gfs_tool
command, all current tunable parameters
including
atime_quantum
(default is 3600 seconds) are displayed.
The
gfs_tool
settune
command is used to change the
atime_quantum
parameter
value. It must be set on each node and each time the file system is mounted. (The set-
ting is not persistent across unmounts.)
5.9.2.1. Usage
Displaying Tunable Parameters
gfs_tool
gettune
MountPoint