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Chapter 6. Clustering
Pacemaker
now supports alert agents
You can now create
Pacemaker
alert agents to take some external action when a cluster event occurs. The cluster passes information about the event to the agent by means of environment variables. Agents can do anything desired with this information, such as send an email message, log to a file, or update a monitoring system. For information on configuring alert agents, see the Red Hat Enterprise Linux 7 High Availability Add-On Reference: https://access.redhat.com/documentation/en-US/Red_Hat_Enterprise_Linux/7/html/High_Availability_Add-On_Reference/index.html. (BZ#1315371)
Pacemaker
now supports SBD
fencing configuration
The
SBD
daemon integrates with Pacemaker
, a watchdog device, to arrange for nodes to reliably self-terminate when fencing is required. This update adds the pcs stonith sbd
command to configure SBD
in Pacemaker
, and it is now also possible to configure SBD
from the web UI. SBD
fencing can be particularly useful in environments where traditional fencing mechanisms are not possible. For information on using SBD
with Pacemaker
, see the following Red Hat Knowledgebase article: https://access.redhat.com/articles/2212861. (BZ#1164402)
Graceful migration of resources when the pacemaker_remote
service is stopped on an active Pacemaker Remote node
If the
pacemaker_remote
service is stopped on an active Pacemaker Remote node, the cluster will gracefully migrate resources off the node before stopping the node. Previously, Pacemaker Remote nodes were fenced when the service was stopped (including by commands such as yum update
), unless the node was first explicitly taken out of the cluster. Software upgrades and other routine maintenance procedures are now much easier to perform on Pacemaker Remote nodes.
Note: All nodes in the cluster must be upgraded to a version supporting this feature before it can be used on any node. (BZ#1288929)
A Pacemaker
cluster resource that is used to create a guest node may now be a member of a resource group
Previous
Pacemaker
versions did not support including a guest node in a group. As of Red Hat Enterprise Linux 7.3, a Pacemaker
cluster resource such as VirtualDomain
that is used to create a guest node may now be a member of a resource group. This can be useful, for example, to associate a virtual machine with its storage. (BZ#1303765)
pcsd
now supports setting SSL options and ciphers
Previously, the
pcsd
service did not enable the user to easily disable a cipher or a particular version of the SSL or TSL protocol if a vulnerability was found of if the protocol version or the cipher was considered weak for some reason. With this update, the user can easily configure SSL options and ciphers in pcsd
, and RC4 ciphers as well as TLS protocol version 1.1 and earlier are disabled by default. (BZ#1315652)
pcs
now supports setting expected votes on a live cluster
When nodes fail in a cluster, user sometimes needs to manually lower expected votes in order to recover the cluster. You can now use the
pcs quorum expected-votes
command to set expected votes on a live cluster. (BZ#1327739)
Support added for configuring Pacemaker utilization attributes
You can now configure Pacemaker utilization attributes with the
pcs
command and the pcsd
Web UI. This allows you to configure the capacity a particular node provides, the capacity a particular resource requires, and an overall strategy for placement of resources. For information on utilization and placement strategy, see https://access.redhat.com/documentation/en-US/Red_Hat_Enterprise_Linux/7/html/High_Availability_Add-On_Reference/index.html. (BZ#1158500)