Using vSphere Host Groups with Enterprise PKS
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This topic describes how to use vSphere Host Groups with Enterprise Pivotal Container Service (Enterprise PKS).
In vSphere, a cluster is a collection of EXSi servers that run virtual machines (VMs). A typical way to organize resources within a cluster is using resource pools. A resource pool is a collection of vSphere resources.
Another way to segment resources within a cluster is using host groups. This means that within a cluster object you can specify certain ESXi hosts to be part of a host group.
Enterprise PKS users can define host groups in vSphere, then in the PKS tile can specify the host group. Host groups align with the Availability Zone (AZ) construct in BOSH, and allow for stretch vSAN clustering.
For more information on vSphere host groups, refer to the vSphere documentation.
This subsection describes use cases for using host groups with Enterprise PKS.
Enabling Support for vSphere Stretched Clusters
A stretched cluster is a single compute cluster that spans two physical datacenters. vSAN is “stretched” to provide storage for the single compute cluster across both physical datacenters.
Host groups support stretched clusters. Kubernetes nodes disks components and PVs will be replicated across the two sites. Kubernetes node VMs can be placed in one site or in both, depending on how the plan is configured (1 AZ checked or 2 AZs checked).
Note: Enterprise PKS supports the default Storage Policy Based Management set on vCenter for vSAN. The number of Failures to Tolerate (FTT) must be set to 1 to perform data replication across the two sites.
Enabling Support for vSAN Fault Domains
The vSAN fault domains feature instructs vSAN to spread redundancy components across the servers in separate computing racks. In this way, you can protect the environment from a rack-level failure such as loss of power or connectivity. For more information, see Designing and Sizing vSAN Fault Domains in the VMware documentation.
Fault domains map to host groups. If you have set up fault domains in your vSAN architecture, you can now leverage host groups with PKS.
Using Host Group as a New AZ in BOSH
Previously, the two types of AZs available with PKS on vSphere were Datacenter and Datacenter plus Resource Pool. Host groups gives you a third option: Datacenter plus HostGroups.
In the case of multi-master Kubernetes clusters, with the Datacenter and Datacenter plus Resource Pool AZs, there is no guarantee that master nodes will reside on separate ESXi hosts. With the Datacenter plus HostGroups AZ you can guarantee that Kubernetes master nodes will reside on separate ESXi hosts.
To implement host groups with Enterprise PKS, the first step is to define a host group in vSphere.
- Log in to vCenter.
- Select the compute Cluster.
- Select the Configure tab.
- Under Configuration, select VM/Host Groups.
- Click Add and configure the host group as follows:
- Name: Enter a name for the host group.
- Type: Select Host Group from the drop down.
- Click Add and select the ESXi host(s) to include in the host group.
- Click OK.
- Once done, you should see that the host group is configured.
Once the host group is defined in vSphere, the next step is to declare this host group when defining the BOSH Availability Zone (AZ) for use with Enterprise PKS.
- Log in to Ops Manager.
- Select the BOSH Director tile.
- Select the Create Availability Zones tab.
- Select the desired AZ, or create a new one.
- In the Clusters section, enter the name of the Host Group.
- Click Save.
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