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10.2. Tune GFS
When
updates are enabled, GFS (by default) only updates them once an hour. The time
atime
quantum is a tunable parameter that can be adjusted using the
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
the frequency of
atime
work loads.
To see the current values of the GFS tunable parameters, including
use the
gfs_tool gettune
The default value for
atime_quantum
The
gfs_tool settune
must be set on each node and each time the file system is mounted. The setting is not
persistent across unmounts.
Usage
Changing the
atime_quantum
gfs_tool settune MountPoint atime_quantum Seconds
MountPoint
Specifies the directory where the GFS file system is mounted.
Seconds
Specifies the update period in seconds.
Example
In this example, the
atime
system on mount point
gfs_tool settune /gfs atime_quantum 86400
11. Suspending Activity on a File System
You can suspend write activity to a file system by using the
Suspending write activity allows hardware-based device snapshots to be used to capture the file
system in a consistent state. The
Quantum
atime
, then
atime
updates may cause performance degradation in clusters with heavy
, as described in
Section 4, "Displaying GFS Tunable
is 3600 seconds.
command is used to change the
Parameter Value
update period is set to once a day (86,400 seconds) for the GFS file
.
/gfs
gfs_tool unfreeze
Suspending Activity on a File System
gfs_tool
updates are written more frequently. Increasing
atime_quantum
atime_quantum
gfs_tool freeze
command ends the suspension.
command.
, you can
Parameters".
parameter value. It
command.
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