We are hearing about a number of VSAN stretched cluster implementations going on at the moment, which is great news. I just set up such a configuration once again in my lab as we look at some various scenarios for the next release of VSAN. Now, for anyone looking at implementing VSAN stretched cluster, there is the VSAN 6.1 stretched cluster guide which should be your first port of call. However I noticed that once VSAN stretched cluster is implemented, you get a few warnings that you typically wouldn’t see in standard VSAN deployments. That is what I want to…
In a previous post, I talked about how vSphere HA is used extensively in VSAN Stretched Cluster. The primary purpose of vSphere HA is to restart virtual machines in the event of a failure. However to ensure that the restarted virtual machines continue to perform optimally, and to continue using a warmed cache, I mentioned that we need to use VM/Host affinity rules to achieve this. In this post I want to discuss the role of DRS and VM/Host affinity rules in more detail, and how they are used in VSAN stretched cluster.
Many regular readers will know that we do not do read locality in Virtual SAN. For VSAN, it has always been a trade-off of networking vs. storage latency. Let me give you an example. When we deploy a virtual machine with multiple objects (e.g. VMDK), and this VMDK is mirrored across two disks on two different hosts, we read in a round-robin fashion from both copies based on the block offset. Similarly, as the number of failures to tolerate is increased, resulting in additional mirror copies, we continue to read in a round-robin fashion from each copy, again based on…
As part of the enhancements to Virtual SAN 6.1, stretched cluster support was announced. To provide availability for virtual machines in a VSAN Stretched Cluster, vSphere HA needs to be configured. This allows VMs to be restarted on the same site (with affinity rules) when there is a host failure, or restarted on the remote site when there is a complete site failure. However there are certain settings that need to be configured in a specific way that are fundamental to achieving high availability in a VSAN stretched cluster. In this post, I will call out the VMware recommended settings,…
As part of the Virtual SAN 6.1 announcements at VMworld 2015, VMware announced two new, eagerly anticipated features. The first of these is VSAN stretched cluster, allowing you to protect your virtual machines across data centers, not just racks. And the second is 2-node VSAN, which will be an excellent solution for remote office/branch office (ROBO) configurations. To allow these configuration to work, a dedicated witness host is required. For those of you already familiar with VSAN, a witness component is used in the event of a split brain to figure out if the virtual machine objects have a quorum.…
With the announcements just made at VMworld 2015, the embargo on Virtual SAN 6.1 has now been lifted, so we can now discuss publicly some of the new features and functionality. Virtual SAN is VMware’s software-defined solution for Hyper-Converged Infrastructure (HCI). For the last number of months, I’ve been heavily involved in preparing for the Virtual SAN 6.1 launch. What follows is a brief description of what I find to be the most interesting and exciting of the upcoming features in Virtual SAN 6.1. Later on, I will follow-up with more in-depth blog posts on the new features and functionality.