---
date: 2013-09-05
title: Open Source Virtual SAN thought experiment
category: Opinions
---

Okay, I know I am little slow on the uptake here, but I was on holiday
at the time. The announcement of [Virtual
SAN](https://www.vmware.com/products/virtual-san/) at VMWorld the last
week got me thinking a bit.

Very briefly, Virtual SAN takes locally attached storage on you
hypervisors. It then turns it into a distributed object storage system
which you can use to store your VMDKs.
[Plenty](https://www.yellow-bricks.com/2013/09/05/how-do-you-know-where-an-object-is-located-with-virtual-san/)
[of](https://www.computerweekly.com/news/2240166057/VMware-Virtual-SAN-vision-to-disrupt-storage-paradigm)
[other](https://chucksblog.emc.com/chucks_blog/2013/08/considering-vsan.html)
[people](https://architecting.it/2013/08/29/reflections-on-vmworld-2013/)
have gone into a lot more detail. Unlike other systems that did a
similar job previously this is not a Virtual Appliance, but runs on the
hypervisors themselves.

The technology to do this sort of thing using purely Open Source exists.
All this has added is a distributed storage layer on each hypervisor.
There are plenty of these exist for Linux, with my preference probably
being for GlusterFS. Something like this is what I would have in mind:

{% img center <https://i.imgur.com/NHYdf78.png> %}

Ceph is probably the closest to Virtual SAN, as it is fundamentally
object-based. Yes there would be CPU and RAM overhead, but that also
exists for Virtual SAN too. Something like DRBD/GFS2 is not really
suitable here, because it will not scale-out as much. You would not have
to have local storage in all your hypervisor nodes (as with Virtual SAN)
too.

I honestly do not see any real problems with this.
