红帽全球峰会第 27 章 Configuring quorum devices
You can allow a cluster to sustain more node failures than standard quorum rules allows by configuring a separate quorum device which acts as a third-party arbitration device for the cluster. A quorum device is recommended for clusters with an even number of nodes. With two-node clusters, the use of a quorum device can better determine which node survives in a split-brain situation.
You must take the following into account when configuring a quorum device.
- It is recommended that a quorum device be run on a different physical network at the same site as the cluster that uses the quorum device. Ideally, the quorum device host should be in a separate rack than the main cluster, or at least on a separate PSU and not on the same network segment as the corosync ring or rings.
- You cannot use more than one quorum device in a cluster at the same time.
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Although you cannot use more than one quorum device in a cluster at the same time, a single quorum device may be used by several clusters at the same time. Each cluster using that quorum device can use different algorithms and quorum options, as those are stored on the cluster nodes themselves. For example, a single quorum device can be used by one cluster with an
ffsplit(fifty/fifty split) algorithm and by a second cluster with anlms(last man standing) algorithm. - A quorum device should not be run on an existing cluster node.
27.1. Installing quorum device packages
Use to following procedure to install the packages you require for configuring a quorum device for a cluster.
Procedure
Install
corosync-qdeviceon the nodes of an existing cluster.[root@node1:~]# dnf install corosync-qdevice [root@node2:~]# dnf install corosync-qdeviceInstall
pcsandcorosync-qnetdon the quorum device host.[root@qdevice:~]# dnf install pcs corosync-qnetdStart the
pcsdservice and enablepcsdat system start on the quorum device host.[root@qdevice:~]# systemctl start pcsd.service [root@qdevice:~]# systemctl enable pcsd.service
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