---
date: 2013-02-21
title: Something from the shadows
category: Opinions
---

An intriguing startup came out of stealth mode a few days ago. [Pernix
Data](https://pernixdata.com/) was founded by Pookan Kumar and Satyam
Vaghani, both of who were pretty near top of the pile in VMware\'s
storage team.

What they are offering is, to me at least, a blinding flash of the
obvious. It is a softweare layer that runs on a VMware hypervisor that
uses local flash as a cache for whatevery is coming off your main
storage array. {% img right
[https://pernixdata.com/images/home\\\_graphic3.png](https://pernixdata.com/images/home\_graphic3.png)
300 217 %}. That could be an SSD (or multiple) or a PCI-e card.

Reading what they have to say, it is completely transparent to the
hypervisor, so everything just works. Obviously me being an Open Source
fanatic I imediately started thinking how I could do this with Linux; it
took me about 5 minutes.

You take your SAN array and give your LUN to your Hypervisors (running
KVM obviously, and with a local SSD). Normally you would stick a
clustered file system (such as GFS2) on that shared LUN. Instead you use
a tiered block device on top of that LUN. There are two that come
immediately to mind:
[Flashcache](https://github.com/facebook/flashcache/) and
[Btier](https://sourceforge.net/projects/tier/files/).

Finally, you can put your clustered file system on that tiered device. I
do not have the time or facilities to test this, but I cannot see why it
would not work. Maybe someone at Red Hat (seeing as they do the bulk of
KVM and GFS2 development) can run with this and see what happens. What
their plans are I do not know. It is very early days, maybe they will be
a success maybe not. As they are both ex-VMware, I would not be at all
surprised if they get bought back into the VMware fold. Certainly this
is a functionality that I would have like to have seen in the past.
