Q&A: Xen, the start-up in Citrix clothing

It's been a year since Citrix bought XenSource, the company created by the founders of the Xen open-source hypervisor, and integrated the business into its lineup of products delivering applications to desktops.

As part of the process, Citrix made the XenServer virtualization software central to its strategy, and appointed XenSource staff to senior executive positions.

ZDNet UK sat down with one of those executives, Ian Pratt, Citrix's vice president for special products, to find out how the integration is going and where Citrix is going with Xen-branded products.

In the second half of our two-part interview, Pratt talks about the impact of the Citrix takeover, the competitiveness and future of Xen, and more generally about the prospects for virtualization in a recession. (For part one, see "Q&A: Citrix exec says cloud to carry Xen against VMware.")

Tell me what's been happening in the past year. You've gone from being an independent company to becoming part of Citrix. But from the outside, it sometimes looks more as if Xen has taken over Citrix. Half the company's products have been renamed--Metaframe became XenApp and Desktop Server became Xen Desktop--Simon Crosby is now chief technology officer, and you're vice president for advanced products.
Pratt: Well, we've benefited from a larger channel. There are 5,000 people selling Citrix. But we don't immediately get 20 times the volume--there's a lot of training to be done. XenSource has been doubling sales every quarter, quite happily. Now as a start-up, we thought we expected to multiply by 100 every quarter, but doubling our sales is just fine.

We are seeing real benefits from integrating with the Citrix technology. We can make sure that (Citrix's) Xen Desktop works well with XenServer, for example. XenSource is now a new division in Citrix, for virtualization management. The chief executive (Peter Levine) is now a senior vice president--and both Simon and I report to him.

In fact, we haven't changed that much. There is more process in a bigger company, but from an engineering point of view, we are the same set of folks who wake up every morning wanting to stick it to VMware. We still have a start-up feeling.

Have you been asked to become more commercial? Have you had to go over to "the dark side"?
Pratt: In Citrix, we have not been asked to do anything against our genes. The open-source community has no problem with what we are doing.

Xen.org is being run the same way as it was before--but one thing Citrix has done is to fund a full-time project manager for Xen.org. If Xen got a bad reputation it would not in any way help Citrix.

It's not the only open-source hypervisor, though. Red Hat has been talking of the advantages of KVM, having bought Qumranet, its creator. Among other things, they say it will have long-term benefits from being integrated upstream with the Linux kernel.
Pratt: KVM is an add-on to the Linux kernel. It's hosted, not a true Type 1 hypervisor. It can never be a true Type 1 hypervisor. (Editors note: A Type 1 hypervisor runs on the bare metal of the server, while a Type 2 hypervisor is hosted on an operating system. Both VMware ESX and Microsoft Hyper-V are Type 1 hypervisors.)

With KVM you have the whole of Linux in the trusted layer. That includes device drivers and so on. And that is bad.

We also have broader support. You don't have to have Linux to run Xen. It runs on Solaris or BSD. KVM requires Linux.

Does virtualization itself still have good prospects? Is it the recession-proof part of IT?
Pratt: Everyone is doing it, and they are still doing it. Virtualization is a mature technology and the benefits to the bottom line are clear. You do it to save money, and people will continue doing that. The savings are immediate.

Having said that, some use cases may get pushed further out. For instance, some green sales may get delayed, where the motivation is partly reducing carbon footprint.

That's just where the company's IT power budget isn't reported clearly, surely?
Pratt: Yes. If the chief information officer's budget includes energy usage, then the company is more likely to deploy virtualization. But there are still plenty of companies where energy is treated separately, as part of the facilities budget.

So virtualization isn't absolutely recession-proof. Nothing is. But it has very good prospects.

Now is a good time to have a product that is a better value of solution. It's not a good time to be buying Rolls Royces. It's time to be buying Priuses. (Editors note: Earlier, Chief Technology Officer Simon Crosby compared Xen to a Toyota Prius and VMware to a Rolls Royce.)

As vice president for advanced products, what are you looking at?
Pratt: Client virtualization is an area I'm spending time on. It's an area where Xen leads--despite some bluster from VMware. It's an area where we can make a difference, and it will be driven by application delivery.

There will be virtualized smartphones on the market in the not-too-distant future. ARM has built virtualization into its processors; they didn't put that in for fun.

Virtualization in the embedded market will follow a similar playbook to virtualization in the x86 market. Client virtualization is going to happen quite quickly. It won't go through the phase where users have to choose their virtualization solution, because virtualization won't exist as a category. It will be part of the device when you buy it.

My other main area of interest is cloud computing. Between client and cloud, I have quite enough to do. They are both areas where Xen is a leader, and historically any area that wins on the client, ends up winning on the server.

A Xen presence on clients will bolster what we are doing on the server. And the cloud will help Xen, because it makes it easier to move virtual machines into the cloud. It will be possible to bridge from the cloud to the enterprise, so resources can be added dynamically.

Why pay for machines in the server room, when you can push them out into the cloud? In particular, functions like test and development, and disaster recovery, can be in the cloud. And if that cloud and the server room are both Xen, then it is much easier to do.

Peter Judge of ZDNet UK reports from London.