Virtualization Technology News and Information
Interview with Virsto Software CEO Mark Davis: Virsto One v1.2

Virsto Software hit the virtualization scene back in February 2010 with its innovative storage solutions for virtual servers... specifically, the company chose to attack the storage I/O problems of Microsoft Hyper-V first.  Evidently, it can be better to be a problem solver and a big fish in a small pond rather than a small fish in the ocean.  Especially if you believe that small pond is about to expand into another large body of water at some point in the near future.

This week, Virsto announced a new version of its popular Virsto One software, bringing it to version 1.2.  It will add advanced support for Microsoft datacenter and infrastructure solutions, including Microsoft Windows Server 2008 Hyper-V R2 and Microsoft System Center, through its work with Microsoft as a Microsoft System Center Alliance partner. The new release also supports Microsoft System Center Data Protection Manager 2010, Microsoft System Center Virtual Machine Manager 2008 and Microsoft Volume Shadow Copy Service (VSS).  And it also complements the recently announced Hyper-V Dynamic Memory feature in Microsoft Windows Server 2008 R2 service pack 1, which enables greater virtual machine density by optimizing available memory for servers and desktop virtualization deployments. 

To find out more, I had the opportunity to speak with Mark Davis, Virsto Software's CEO.  The new release of Virsto One is largely about increased support for Microsoft System Center technologies.  Are you adding these new features in response to market demand, or are you getting pressure from Microsoft?

Davis:  Customer requests are driving us. A lot of our early customers use System Center software to manage their Hyper-V systems, so we've joined Microsoft's System Center Alliance.

A significant percentage of our customers use System Center Virtual Machine Manager (VMM) to monitor and control their Hyper-V servers, and virtual machines built on Virsto VHDs (virtual hard disks) can be started, stopped, and monitored using VMM.  We've also integrated into the Rapid Provisioning feature of VMM to dramatically speed up the time to provision a new VM from a template library. Normally, the process involves reading the template from the library server's disk repository, copying gigabytes across the network, and then writing the template image to new storage. With Virsto One, Rapid Provisioning can invoke our ability to instantly clone a VHD image and make it available anywhere in the network. This can take tens of minutes out of every VM provisioning operation. Because Rapid Provisioning is scriptable, there is a lot of flexibility.

We've also been asked by customers to integrate with Microsoft System Center Data Protection Manager (DPM). In Virsto One v1.2, released this week, we have a solution that makes DPM even faster, taking advantage of our unique high performance snapshotting facilities.  You say that Virsto One complements Microsoft Dynamic Memory to increase the number of virtual machines that can be run per physical server.  Can you explain how that works?

Davis:  Dynamic Memory is a new feature of Microsoft Windows Server 2008 R2 Service Pack 1. Without going into the details, Dynamic Memory allows you to run more Hyper-V virtual machines in a given amount of memory. This is important because increasing VM density - the ratio of VMs per physical server - is an important goal of any virtualization project.

How does that relate to Virsto One? Well, with Microsoft Dynamic Memory alleviating memory bottlenecks, another major bottleneck becomes more visible.

Storage I/O is often choked on hypervisors. The culprit is the "VM I/O Blender". Virsto One solves this problem, so you can get the full I/O throughput your server and storage solutions are capable of, without upgrading hardware. In installations ranging from high end Fibre Channel SANs to low cost commodity direct attached storage, our customers have tripled their potential I/O throughput by adding Virsto One software to their existing systems.

Our friends at Intel and AMD take good care of CPU bottlenecks. Memory bottlenecks are being relieved with technologies like Dynamic Memory. The last hurdle to high VM density is getting rid of the storage I/O bottleneck, which is what Virsto One does.  Can you tell us more about what the "VM I/O Blender" is all about?  And does it affect all hypervisors, or does it just affect Hyper-V?

Davis:  The VM I/O Blender is, regrettably for virtualization users, quite easy to demonstrate on all virtualization platforms. It is inherent in the way hypervisors work, and a storage infrastructure that is not built from scratch to deal with it is unlikely to be a real solution.

The VM I/O Blender is the result of running numerous operating system images simultaneously on a single box. Each OS instance tries to optimize its I/O stream for performance, but the hypervisor multiplexes them, presenting highly random I/O that thrashes storage hardware.

The result is that as you add VMs to a server, the total I/O throughput of the box goes down. On a loaded server, half, even 80% or more, of the server and storage hardware's I/O capacity is sapped. As a result, achievable VM density is constrained by I/O, even though the hardware is capable of delivering much more performance.  What advice would you give to an IT manager looking for a storage solution right now that helps with VM sprawl?

Davis:  Don't throw hardware (and money) at the problem.

Everybody who virtualizes experiences VM sprawl. We end up with enormous numbers of VMs, occupying gigabytes (often tens of gigabytes) of disk space each. So everyone talks about using space saving techniques like thin provisioning, cloning, and deduplication.

The problem is that the performance characteristics of many thin provisioning, cloning, or dedupe solutions make them unusable in production. What is the point of these features if you can't use them in I/O intensive production workloads?

By far the most common solution is to buy more hardware to solve the problem. We heard from a reseller partner how a large IT shop was forced to spend US$900K on special flash based hardware caches to add to their already expensive storage arrays to get the performance they needed. By the time they paid for software licenses, etcetera, over a million incremental, unplanned dollars were spent to resolve the performance weaknesses of space-saving technologies.

There are ways to get both space savings and high performance storage in virtualization. But it does require a solution that is built from the ground up for the unique needs of VM storage.


I want to once again thank Mark Davis for taking time out of his busy schedule to speak with me about Virsto's latest announcement, and for talking to us more about the VM I/O Blender.

Published Thursday, September 16, 2010 6:20 AM by David Marshall
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