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vSphere HA and DRS over iSCSI SAN

vSphere features HA, vMotion and DRS ensure high availability and optimum resource distribution of workloads (VMs) running on ESXi hosts in a target Hosts cluster. The compute resource for these workloads (CPU, RAM, GPU) are claimed from the host on which the workload is running.


The storage on which these workloads reside is slightly different. For vSphere features such as HA, vMotion and DRS (which in very simple terms is just automated vmotion for optimum resource scheduling) to work, the target hosts in the target cluster must be connected to a shared storage and the VMs which need to be armed with these features must reside on the shared storage.

The shared storage can be vSAN storage; which is VMware's feature for aggregating host storages across a cluster to form a single shared storage; or we can have SANs connected to all the hosts in the cluster. These SANs can be connected over FC, FCoE or simply iSCSI.


In this example, for demo purposes, I have connected my NAS as an iSCSI SAN to 2 nested ESXis in a HA-DRS cluster. Refer to my blog post: "iSCSI and Management traffic on single NIC: For non-production environment only! (virtualmystery.info)" dated 13th June 2021, for details on how to configure the iSCSI SAN to the ESXi hosts. In addition, refer the following Vmware knowlede base article for more information on using ESXi with SAN: "Overview of Using ESXi with a SAN (vmware.com)". You can also refer to the following post for best practices on configuring iSCSI SAN: "Best Practices For Running VMware vSphere On iSCSI | VMware"

Please ensure the SAN is configured in identical manner across all the hosts in the target cluster. In addition, ensure the target workloads' storage reside in this SAN.


In this demo, I have configured an iSCSI SAN to two nested ESXis in a cluster. The cluster has HA and DRS enabled. I have deployed blank (dummy) VMs on the iSCSI SAN datastore. The iSCSI SAN datastore has been named "Demo" and configured with VMFS 6 format. Since the purpose of this demo is to only show the working of HA and DRS on iSCSI SAN; I have only used dummy VMs.



Watch the demo video below to see the HA and DRS over iSCSI SAN in action:



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