Red Hat GFS 6.0 -, Руководство администратора

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6 Chapter 1. Red Hat GFS Overview
1.3.2. Lock Management
A lock management mechanism is a key component of any cluster file system. The Red Hat GFS
lock-management mechanism provides the following lock managers:
•
Single Lock Manager (SLM) — A simple centralized lock manager that can be configured to run
either on a file system node or on a separate dedicated lock manager node.
•
Redundant Lock Manager (RLM) — A high-availability lock manager. It allows the configuration
of a master and multiple hot-standby failover lock manager nodes. The failover nodes provide
failover in case the master lock manager node fails.
The lock managers also provide cluster management functions that control node recovery. Refer to
Chapter 8 Using Clustering and Locking Systems for a description of the GFS lock protocols.
1.3.3. Cluster Management, Fencing, and Recovery
Cluster management functions in GFS monitor node status through heartbeat signals to determine
cluster membership. Also, cluster management keeps track of which nodes are using each GFS file
system, and initiates and coordinates the recovery process when nodes fail. This process involves
recovery coordination from the fencing system, the lock manager, and the file system. The cluster
management functions are embedded in each of the lock management modules described earlier in
Lock Management. Refer to Chapter 8 Using Clustering and Locking Systems for more information
on cluster management.
Fencing is the ability to isolate or "fence off" a cluster node when that node loses its heartbeat no-
tification with the rest of the cluster nodes. Fencing ensures that data integrity is maintained during
the recovery of a failed cluster node. GFS supports a variety of automated fencing methods and one
manual method. In addition, GFS provides the ability to configure each cluster node for cascaded
fencing with the automated fencing methods. Refer to Chapter 10 Using the Fencing System for more
information about the GFS fencing capability.
Warning
Manual fencing should not be used in a production environment. Manual fencing depends on human
intervention whenever a node needs recovery. Cluster operation is halted during the intervention.
Recovery is the process of controlling reentry of a node into a cluster after the node has been fenced.
Recovery ensures that storage data integrity is maintained in the cluster while the previously fenced
node is reentering the cluster. As stated earlier, recovery involves coordination from fencing, lock
management, and the file system.
1.3.4. Cluster Configuration Management
Cluster configuration management provides a centralized mechanism for the configuration and
maintenance of configuration files throughout the cluster. It provides high-availability access to
configuration-state information for all nodes in the cluster.
For
information about cluster configuration management refer
to Chapter 6 Creating the Cluster Configuration System Files and
Chapter 7 Using the Cluster Configuration System .