In case of disaster, an Entrust PKI Hub installation with N nodes is available if at least (N/2)+1 nodes are available. This minimum number of working nodes is referred to as "quorum".

When deploying Entrust PKI Hub in high availability, we recommend 3 or 5 nodes because:

  • A 2-node installation fails when a single node fails.
  • A 4-node installation fails when 2 nodes fail, just like a 3-node installation.  Adding a node to an odd number of nodes does not increase the number of tolerated node failures. 
  • Entrust PKI Hub does not support more than 5 nodes.

See the table below for the supported node failures.

Cluster nodes

Nodes alive

Nodes broken

Quorum

3

1

2

(error)

3

2

1

(tick)

5

1

4

(error)

5

2

3

(error)

5

3

2

(tick)

5

4

1

(tick)