There was a great turn out for the joint Citrix and Marathon Webinar today, The “Best of VMWorld Approach” to Virtualization and Availability. Thanks to everyone for attending. If you missed it or want more information visit here to download the presentation.

There were a lot of great questions for Simon Crosby and Jerry Melnick, which we have captured below. If anyone has any additional questions, feel free to leave a comment here on the blog or contact us directly.

Simon: Do you need 64-bit hardware to try out the express edition?

All modern server hardware is 64 bit enabled. Xen uses all of the modern features of Intel VT or ANDV to perform hardware virtualization of Windows; so the answer is yes but if you have a modern server you’re in good shape.

Jerry: How does everRun VM’s second level of availability differ from VMware HA?

One of the key pieces is that we compute through the failures of any I/O fault or failure, and then automatically redirect I/O to the device that survives it. In VMware HA, the failure of an I/O device isn’t necessarily detected or managed it’s just host failure. We are managing virtual machine failures in related I/O devices.

The second piece is that we’re doing active validation of all the devices so that we know at all times if all the resources are available and that they can actually be utilized in the case of recovery. If you don’t have active validation, such as with VMware HA, you can failover your VM and get to the other side but you may find that the device which handles the disk isn’t actually operational because of either a failure in the hardware or some kind of problem administratively with how you configured it.

Simon: Is there an extra cost associated with XenCenter?

No, it’s just a pre-feature of the product. Our architecture does not require something like virtual center because every server in the resource pool redundantly has every piece of information for the entire resource pool. Should any server fail, we automatically elect a pool leader from the remaining servers and all mainstream information is highly available as a result.

XenCenter itself is a perfect thin client UI which interfaces with as many resource pools as you want to run, but it is literally a thin UI – it’s stateless, and all of the state related to managing the infrastructure is in the infrastructure itself, which allows us to really scale this architecture.

Jerry: In the demonstration you gave, are users hitting both hosts in the exchange application being protected?

In the level 3 fault tolerance configuration we are running both hosts redundantly which is what you need to do for full system-level fault tolerance. In level 2 the amount of resource being utilized is less because you’re actually only running a virtual machine on one of the hosts, but you’re running I/O on both of the hosts. In level one you’re running at the next level down, with only a single VM allocated and no preallocation of the secondary side, with all I/O processing on just that one side. There is no active redundancy. That’s why we provide the different levels; so that you can choose which virtual machines really need to use that resource and have that ability, and which ones you want to make some trade-offs of availability versus resource utilization.

Simon: What does it mean to have a 64-bit hypervisor and why is that better?

If you have a 64-bit hypervisor then you can host both 32 and 64-bit guests and you don’t have any issues really to address space conversion problems. It’s a cleaner architecture, the memory architecture scales massively up to four terabytes (not that you can buy a server that has four terabytes of thin slots), but it allows us to massively scale the memory and CPU of the system. We support up to 32 physical CPUs and a box as a result, and we have an architecture that is going to scale superbly for us.

Jerry: Do you need a dedicated LAN to run everRun VM?

The only dedicated LAN we use, and can actually be shared because of the flexibility of XenServer itself, is what we call the availability link which is part of our best practices. Otherwise it’s all a standard LAN configuration that you would have in the XenServer pool.

Jerry: Are there certain applications that are not suited for everRun?

Our technology is completely transparent – relative to the application itself. Any windows application that you run on a Windows VM can be run by our technology.

Jerry: Is it possible to combine XenMotion with everRun VM?

As part of our capability, the ability of motion of VM from one host to the next is extremely integral to it. You get the capabilities to provide recovery from failures as well as to be able to have planned downtime and migrate your VMs when you want to do a repair. It’s an integral part of the product and we use XenMotion as the backbone of it. One difference with everRun VM is that we allow this motion capability without the need for a shared-LUN, or SAN, storage subsystem.

Simon: How would a current ESX 3.x customer migrate to a Xen environment and why should they do that?

There are free tools available to do this which can be downloaded off our forums and indeed Microsoft has similar free tools available. Here’s why you would do it: we guarantee that Citrix XenServer VMs are literally compatible with Microsoft Hyper-V. They’re also compatible with every other Xen implementation. What I see emerging is essentially two camps: A camp in which there is an open architecture (Microsoft storage architecture is very similar to XenServer, it’s also an open architecture) where you’ll have a bunch of virtual infrastructures out there from different vendors all of which are interoperable; and then a camp where there’s VMware.

The reason to move to XenServer is that we are fundamentally focused on a rich ecosystem of value added providers. We are diametrically opposed to an architecture which presumes that everything comes from one vendor, and where the entire architecture is dictated to you. The moment you invest in an architecture which is one size fits all (cost aside) you will find that it has limitations.

I am starting to see that the one size fits all architecture, which has done VMware a great favor for its first 10-15% of the market, is starting to show signs of age as we look at new use cases. For example, for desktop virtualization or for high availability, you can’t do this with that architecture and its no surprise then that at VMWorld the awards for innovation go to open architecture and best of breed vendors – Marathon at VMWorld winning the award for fault tolerance. We are dedicated to an open architecture and best of breed.

Jerry: Is Marathon planning to protect Linux based VMs in the near future?

Our road map will extend over the next year to protect all the hosts that are supported by XenServer.

Simon: Can you give a rough idea of the performance overhead of a virtual server vs. a real server?

It’s highly dependent on the workload. Typically we see between .5% and 2% overhead even for very I/O intensive workloads. For Windows it’s notionally higher. The great thing about this is that we are writing the hardware code; unlike my friends at VMware who are still tied to software implementation of virtualization in which they have to patch the binary of a running guest operating system. We ride the hardware improvement curve of Intel and AMD. What we’ve seen there is roughly a three-fold performance increase per year. Typical overheard for virtualizing Windows guests is around 3-5%. The most intensive workload I have ever seen is in fact Windows Terminal Services or our own Citrix Presentation Server where we currently stand at about 8% overhead.

Jerry: Does everRun VM support shared storage?

Yes. We actually support any capability in storage. Whatever kind of LUN that you can present to XenServer and carve up into a storage repository or a VHD, we will support that. If it’s a local disk, low-end RAID storage or just a bunch of disks we will support that, as well as high-end SAN storage. The advantage of the product is that we will support local storage for very low-end small environments.

Jerry: How far can the servers be separated?

It is not a matter of actual distance but rather a matter of network connectivity between the two hosts. We have systems currently deployed with separation of greater than 100 miles.