Learn basic to advance vSAN in 80 minutes

Published: General


If you are working in Virtualization and Cloud space, then you must have heard about Software Defined Storage (SDS). It is part of Software-Defined Data Center (SDDC) (a term coined by VMware). Since VMware started the SDDC journey and is a pioneer in this technology, so, today I am going to cover VMware solution in this space. Virtual SAN or vSAN is the solution from VMware which provides SDS capabilities in VMware environment. This post will cover vSAN in detail with a demo at the end. By following this post you will have a clear understanding of vSAN and would be able to utilize it in your environment.


Before we discuss vSAN, let's talk about Software Defined Storage a bit.

In VMware words, Software-defined storage (SDS) abstracts the underlying storage through a virtual data plane, making the VM (and the application) the fundamental unit of storage provisioning and management across heterogeneous storage systems. Also, in the VMware software-defined storage (SDS) model, storage services are dynamically composed and driven by policy. This is accomplished by abstracting the underlying hardware, similar to the server and network virtualization.

Unlike traditional SAN environment, in SDS, the end VM's are of utmost importance. In typical SAN environment, we configure storage first. The endpoints consume storage through configured LUN's.  All VM's residing in the LUN gets the same protection, performance, and incurs same IO penalty. For example, a transactional database will benefit greatly from a LUN backed by RAID10. A typical website with random read/write will benefit from RAID5. Archival data benefits from a RAID6 LUN. We rarely segregate VM's per their IO profile in a traditional enviornment. Which leads to less performing VM's.

Per VM policies and specialized software define storage in SDS environment. So, if a VM hosts a database we can set individual policies according to it. It has no effect on another VM. Thus we benefit greatly from this type of setup. Besides management of these environments are really easy.

Any Doubts?

SDS is generally considered to be slower than traditional storages. The performance of a traditional SAN certainly does not come from capacity disks. Highest performing disks give you 15K RPM. So, whether it is in a storage box or local to a server, performance of a disk remains same. The performance of the storage boxes comes from the large cache they use. Essentially, a storage box runs a specialized software in a dedicated processor and the performance is from the high performing cache tier.

What if we give such a cache tier on every server? In a typical virtualized environment, we don't use the local disks as a capctiy tier. Thus underutilizing resources. We can utilize this storage as capacity tier. For performance, we provide a high performing cache tier on each server. Also, we put a specialized software for handling storage in the hypervisor code. So essentially we mimic a traditional SAN environment. 

A dedicated processor handles data processing in a traditional storage. Though a Hypervisor already handles IO requests for VM's, putting storage decisions in it will place extra load on its resources (about 10%). With careful design and accounting this extra loadremoves the problem. Besides, since Hypervisor now provides both virtualization and storage capabilities, it has greater visibility into the environment and can define policies with more granularity.

Why vSAN?

vSAN has the following advantages:

  • Virtual SAN eliminates the need for an external expensive storage array
  • vSAN is designed specifically for vSphere Administrators. So storage maintenance does not require a special team.
  • Predictive performance is achieved through per VM policies
  • Tier-1 applications can use vSAN storage without any performance issue
  • It is much cheaper than traditional costly storages at the same time providing similar performance
  • Since it is built into industry proven vSphere hypervisor, it is robust
  • Very simple to manage. Enabling it takes a single click
  • Upgrading vSAN is a cakewalk
  • Highly secure

Topics covered

Given below is the list of the topics covered in the session:

  • Overview of vSAN
  • Important terms
  • How it works
  • Simplicity of use
  • Advanced use cases
  • Demo

Specifically, this session will answer the following:

  • Why non-data locality is not a problem in vSAN. Actually, it is an advantage to have
  • How a write and read operation is performed in vSAN in both all-flash and hybrid environment

As always live demo is provided in the session to showcase the information provided in the slides.


The vSAN software is already included in the hypervisor. To use it all you need to do is unlock the capabilities with a license key. It is an amazing technology which makes storage so easy to use. So if you are not actively using it, I hope this session will enable and encourage you to start using it. For more details please check the official VMware site and product documentation.

As always I welcome your feedbacks. Please do share them so that I can fine tune my further sessions.