What, exactly, is the difference between a storage network appliance and storage management software for networks, in terms of performance and reliability? It’s a question The Register famously put to the test last September, pitting network storage hardware from EMC and NetApp against a software-based storage management system from Nexenta – using commercial off-the-shelf (COTS) hardware – costing an order of magnitude less. Its conclusion was that the performance difference wasn’t all that much, which drew furious criticism from EMC. But EMC’s defense drew further suspicion, admitting that it too used COTS hardware for its own storage, and arguing that the differences lay in the processors EMC uses to drive high availability.
Cloud architectures are driving the issue of how everyday, even expendable, storage hardware can be utilized by more efficient, often open source, management software running on very-high-end processors. Now Nexenta, which blew this whole issue wide open, is training its sights on a separate, though slightly related, market: virtual desktops.
Why can’t virtualization be faster?
Next Q1, Nexenta will be generally releasing a unified dashboard for VMware-based virtual desktops, called simply enough, NexentaVDI. Its purpose, as Nexenta CEO Evan Powell explained to RWW, is to automate the deployment of new virtual desktops to the extent that they can be deployed in minutes rather than hours – or, in the case of some enterprises, days.
“I was reading one of the articles you wrote recently where you’re talking about takeaways from the VMware / Intel virtualization chat,” remarked Powell (whom I’m happy to have as a regular reader), “and one of the things you mentioned was, isn’t there some way that virtualization could accelerate certain workloads? And somebody said, ‘Yea, if you could keep the workload local as opposed to sending it out to shared storage.’ NexentaVDI is exactly that use case.”
NexentaVDI utilizes the same engine as the NexentaStor system that matched EMC and NetApp in The Register’s tests, but then adds a simplified UI with tie-ins to VMware View. That UI adds tools for deploying VMs, and then verifying and optimizing their performance levels. “It optimizes dozens, maybe north of a hundred, potential testing and optimization steps that you would take, and then it spits out a report that says, ‘I’ve deployed 150 desktops, or 1,500, and they’re now getting 103 IOPS on the read side,’ whatever the performance is,” the CEO explains.
Addressing the VDI bottleneck issue
“The number one problem in VDI, according to both the Citrix and VMware folks I’ve chatted with, is essentially price/performance of storage,” says Powell. “You end up taking an inexpensive disk in your laptop, putting it in an EMC array, and now you’re running it over a network so it’s generally slower. So you end up with something that is more expensive… The fundamentals I’ve heard are that the ROI models often don’t work. If you’re financials or healthcare, or you’re a hosting company that wants to sell desktops… the economics are in the way.”
VMware has yet to implement a dedicated streaming codec like Citrix’ HDX, so as Powell points out, price/performance can still be an issue with VMware VDI when hundreds or thousands of desktops come into play simultaneously. NexentaVDI addresses this issue directly by creating a local storage array using the ZFS file system made for Solaris, but exclusively for hosting desktops. The software then adds performance monitoring and optimization tools implementable from directly within VMware View. “We felt that it wouldn’t address the pain point if we just hadn’t also had the visibility into performance,” remarks Powell.
For example, how much memory should you give to the main I/O of the VM representing your storage versus the VMs for the desktops? This is one of the trade-offs the tool will enable admins to adjust.
ZFS is already at the heart of Nexenta’s product line. “Dear old Sun put $150 million into developing the ZFS file system, which is now proliferating in the cloud,” he adds. “And we take that file system and wrap around it a bunch of our own software, and turn it into something feature-comparable to an enterprise storage or NAS system from, say, NetApp in terms of ease of use, replication, high availability, all the things that you need to make a system foolproof.”
As we learned earlier this month from our live discussion with virtualization engineers at both Intel and VMware, we’re approaching the time when the performance hit from moving from physical to virtual desktops is near zero. But as VMware’s Steven Shultz told us, it won’t go below zero, to the point where there would be a performance gain. Nexenta’s Powell isn’t so sure about that. By keeping storage local and off the network, he contends, I/O performance for virtual desktops has demonstrated among his customers by as much as 4x. He admits the costs do not decline to 1/4 in turn, but cost savings remain significant.
NexentaVDI itself is deployed as a VM, which makes installation “pretty darn trivial,” as Powell describes it. As the product nears final release in the next quarter, the company is making plans to provide sales and technical training through VMware’s teams. Although NexentaStor has also supported Citrix XenDesktop, for the time being, NexentaVDI will be geared for VMware.