DRS and VM/Host Affinity Groups in VSAN Stretched Cluster

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.

Read locality 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…

Getting started with HCIbench, the benchmark for hyper-converged infrastructure

This week I had the opportunity to roll-out the  HCIbench tool on one of my all-flash VSAN clusters (much kudos to my friends over at Micron for the loan of a bunch of flash devices for our lab). The HCIbench is a tool developed internally at VMware to make the deployment of a benchmark tool for hyper-converged infrastructure (HCI) systems quite simple. In particular, we wanted something that customers could use on Virtual SAN (VSAN). It’s an excellent tool for those of you looking to do a performance test on hyper-converged infrastructures, thus the name HCIbench. Please note that this…

My VMworld Session – VSAN Monitoring & Troubleshooting – now available

Another of the break-out sessions that I presented at VMworld 2015 in San Francisco on Virtual SAN (VSAN) has been recorded and is now available on the VMworld site. I co-presented “STO6228 Monitoring and Troubleshooting Virtual SAN, Current and Future” with Christian Dickmann of VMware, who did the latter part of the session. I do the initial introduction, talking briefly about VSAN, and then the various tools that we now have for monitoring and troubleshooting. Christian then takes the stage to talk about how things have progressed over the past year, certain use cases and some future plans we have…

VSAN 6.1 New Feature – Handling of Problematic Disks

The more observant of you may have observed the following entry in the VSAN 6.1 Release Notes: Virtual SAN monitors solid state drive and magnetic disk drive health and proactively isolates unhealthy devices by unmounting them. It detects gradual failure of a Virtual SAN disk and isolates the device before congestion builds up within the affected host and the entire Virtual SAN cluster. An alarm is generated from each host whenever an unhealthy device is detected and an event is generated if an unhealthy device is automatically unmounted. The purpose of this post is to provide you with a little…

vSphere HA settings for VSAN Stretched Cluster

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,…