VSAN Part 15 – Multicast Requirement for networking – Misconfiguration detected

This is an issue which has caught a number of customers out during the Virtual SAN beta, so will probably catch some folks out when the product goes live too. One of the requirements for Virtual SAN (VSAN) is to allow multicast traffic on the VSAN network between the ESXi host participating in the VSAN Cluster. However, as per our engineering lead on VSAN, multicast is only used for relatively infrequent metadata operations. For example, object creation, change in object status after a failure and publication of statistics such as a significant change of free disk space (the publication of…

VSAN Part 14 – Host Memory Requirements

For those of you participating in the VMware Virtual SAN (VSAN) beta, this is a reminder that there is a VSAN Design & Sizing Guide available on the community forum. It is part of the Virtual SAN (VSAN) Proof of Concept (POC) Kit, and can be found by clicking this link here. The guide has recently been updated to include some Host Memory Requirements as we got this query from a number of customers participating in the beta. The actual host memory requirement directly related to the number of physical disks in the host and the number of disk groups…

VSAN Part 11 – Shutting down the VSAN cluster

In a post on the vSphere blog, I spoke about how to use maintenance mode. As a follow on request, a number of people asked me how they should safely shutdown a VSAN cluster. In this post, I will address that question and share my observations. On my three-node VSAN cluster, I had a number of virtual machines as well as a vApp running vCenter Operations Manager VMs. My first step was to shut down all virtual machines in my cluster.

A closer look at EMC ScaleIO

Thanks to our friends at EMC, I was recently given the chance to attend a session on EMC’s new storage acquisition, ScaleIO. This acquisition generated a lot of interest (and perhaps some confusion) as VMware Virtual SAN product seemed to play in that same storage area. My good friend Chad Sakac over at EMC wrote about this some 6 months ago in his evocatively titled blog post VSAN vs. ScaleIO fight! Chad explains where, in his opinion, each product can be positioned and how EMC/VMware customers have a choice of storage options. His article is definitely worth a read.  I…

VSAN Part 10 – Changing VM Storage Policy on-the-fly

This is quite a unique aspect of VSAN, and plays directly into what I believe to be one of the crucial factors of software defined storage. Its probably easier to use an example to explain the concept of how being able to change storage policies on the fly is such a cool feature. Let’s take a scenario where an administrator has deployed a VM with the default VM storage policy, which is that the VM Storage objects should have no disk striping and should tolerate one failure.The layout of the VM could look something like this: The admin then notices…

VSAN Part 9 – Host Failure Scenarios & vSphere HA Interop

In this next post, I will examine some failure scenarios. I will concentrate of ESXi host failures, but suffice to say that a disk or network failure can also have consequences for  virtual machines running on VSAN. There are two host failure scenarios highlighted below which can impact a virtual machine running on VSAN: An ESXi host, on which the VM is not running but has some of its storage objects, suffers a failure An ESXi host, on which the VM is running, suffers a failure Let’s look at these failures in more detail.

VSAN Part 8 – The role of the SSD

I will start with a caveat. The plan is to support both Solid State Disks and PCIe flash devices on VSAN. However, for the purposes of this post, I will refer to this flash resource as an SSD for simplicity. SSDs serve two purposes in VSAN. They act as both a read cache and a write buffer. This dramatically improves the performance of virtual machines running on the vsanDatastore. In some respects VSAN can be compared to a number of ‘hybrid’ storage solutions in the market, which also use a combination of SSD & HDD to boost the performance of…