Red Hat Cluster Suite, Руководство пользователя

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Chapter 1. Red Hat Cluster Manager Overview 3
network-accessible database cluster service is usually assigned an IP address, which
is failed over along with the cluster service to maintain transparent access for clients.
The cluster-service framework can also easily extend to other applications through the
use of customized init scripts.
Cluster administration user interface
The Red Hat Cluster Suite management graphical user interface (GUI) facilitates the
administration and monitoring tasks of cluster resources such as the following: creat-
ing, starting, and stopping cluster services; relocating cluster services from one node
to another; modifying the cluster service configuration; and monitoring the cluster
nodes. The CMAN interface allows administrators to individually control the cluster
on a per-node basis.
Failover domains
By assigning a cluster service to a restricted failover domain , you can limit the nodes
that are eligible to run a cluster service in the event of a failover. (A cluster service
that is assigned to a restricted failover domain cannot be started on a cluster node that
is not included in that failover domain.) You can order the nodes in a failover domain
by preference to ensure that a particular node runs the cluster service (as long as that
node is active). If a cluster service is assigned to an unrestricted failover domain, the
cluster service starts on any available cluster node (if none of the nodes of the failover
domain are available).
Data integrity assurance
To ensure data integrity, only one node can run a cluster service and access cluster-
service data at one time. The use of power switches in the cluster hardware configura-
tion enables a node to power-cycle another node before restarting that node’s cluster
services during the failover process. This prevents any two systems from simulta-
neously accessing the same data and corrupting it. It is strongly recommended that
fence devices (hardware or software solutions that remotely power, shutdown, and re-
boot cluster nodes) are used to guarantee data integrity under all failure conditions.
Watchdog timers are an alternative used to ensure correct operation of cluster service
failover.
Ethernet channel bonding
To monitor the health of the other nodes, each node monitors the health of the remote
power switch, if any, and issues heartbeat pings over network channels. With Ethernet
channel bonding, multiple Ethernet interfaces are configured to behave as one, reduc-
ing the risk of a single-point-of-failure in the typical switched Ethernet connection
between systems.
Cluster-service failover capability
If a hardware or software failure occurs, the cluster takes the appropriate action to