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1.2. Before Setting Up GFS2

Before you install and set up GFS2, note the following key characteristics of your GFS2 file systems:
GFS2 nodes
Determine which nodes in the cluster will mount the GFS2 file systems.
Number of file systems
Determine how many GFS2 file systems to create initially. (More file systems can be added later.)
File system name
Determine a unique name for each file system. The name must be unique for all lock_dlm file systems over the cluster. Each file system name is required in the form of a parameter variable. For example, this book uses file system names mydata1 and mydata2 in some example procedures.
Determine the number of journals for your GFS2 file systems. One journal is required for each node that mounts a GFS2 file system. GFS2 allows you to add journals dynamically at a later point as additional servers mount a file system. For information on adding journals to a GFS2 file system, see Section 3.7, “Adding Journals to a File System”.
Storage devices and partitions
Determine the storage devices and partitions to be used for creating logical volumes (using CLVM) in the file systems.
Time protocol
Make sure that the clocks on the GFS2 nodes are synchronized. It is recommended that you use the Precision Time Protocol (PTP) or, if necessary for your configuration, the Network Time Protocol (NTP) software provided with your Red Hat Enterprise Linux distribution.


The system clocks in GFS2 nodes must be within a few minutes of each other to prevent unnecessary inode time stamp updating. Unnecessary inode time stamp updating severely impacts cluster performance.


You may see performance problems with GFS2 when many create and delete operations are issued from more than one node in the same directory at the same time. If this causes performance problems in your system, you should localize file creation and deletions by a node to directories specific to that node as much as possible.
For further recommendations on creating, using, and maintaining a GFS2 file system. see Chapter 2, GFS2 Configuration and Operational Considerations.