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Arbiter

You may also see the arbiter node referred to as a quorum or witness node.

An arbiter node is a cluster member that does not process data but provides stability to cluster technologies. It can run on separate hardware or in a virtual machine. The arbiter node is crucial for high availability in the cluster with two data nodes and ensures cluster stability.

An arbiter node is not required in a cluster setup with three data nodes.

The arbiter node can run on small hardware or in a virtual machine. It cannot be collocated on the same server as another LogMan.io cluster node.

Virtual machine requirements

  • RAM 32 GB
  • SWAP 4 GB
  • CPU 4

Disks
Can be provisioned from the virtualization platform or use LVM to divide disk space to required sections.

  • OS / - 50 GB, thick provisioning
  • Docker /var/lib/docker - 50GB
  • SSD disk /data/ssd - 100 GB
  • HDD disk /data/hdd - 100 GB

Operating System
Ubuntu LTS 22.04 (or its minimal version)

Why is the Arbiter important

Multiple cluster technologies in LogMan.io use election algorithms to assign a master node. Only with odd number (2n - 1) of nodes in the cluster the election can have only one winner. All the technologies are equipped with scenarios how to work in cluster with even number of nodes. However, providing the odd number of nodes brings stability, especially during incidents when one of the cluster nodes might be disconnected.