The management cluster design determines the number of hosts and vSphere HA settings for the management cluster.

Management Cluster Design Decisions

Decision ID

Design Decision

Design Justification

Design Implication

SDDC-VI-VC-014

Create a management cluster with 4 hosts.

Three hosts are used to provide n+1 redundancy for the vSAN cluster. The fourth host is used to guarantee n+1 for vSAN redundancy during maintenance operations.

Additional host resources are required for redundancy.

SDDC-VI-VC-015

Configure Admission Control for 1 host failure and percentage based failover capacity.

Using the percentage-based reservation works well in situations where virtual machines have varying and sometime significant CPU or memory reservations.

vSphere 6.5 automatically calculates the reserved percentage based on host failures to tolerate and the number of hosts in the cluster.

In a four host management cluster only the resources of three hosts are available for use.

SDDC-VI-VC-016

Create a host profile for the Management Cluster.

Utilizing host profiles simplifies configuration of hosts and ensures settings are uniform across the cluster.

Anytime an authorized change to a host is made the host profile must be updated to reflect the change or the status will show non-compliant.

The following table summarizes the attributes of the management cluster logical design.

Management Cluster Logical Design Background

Attribute

Specification

Number of hosts required to support management hosts with no over commitment .

2

Number of hosts recommended due to operational constraints (Ability to take a host offline without sacrificing High Availability capabilities) .

3

Number of hosts recommended due to operational constraints, while using vSAN (Ability to take a host offline without sacrificing High Availability capabilities) .

4

Capacity for host failures per cluster .

25% reserved CPU RAM