Case study: supermarket chooses XenServer over VMware

When U.K. supermarket giant Tesco first explored x86 virtualization 18 months ago, it turned to VMware. But when time came to deploy virtualization in production, Tesco opted for Citrix XenServer, which was approximately half the the cost of VMware and featured the necessary mobility and high-availability features.

Tesco is about two-thirds of the way through a project to virtualize its 1,500 Intel servers on 150 quad-processor, quad-core HP ProLiant BL680c G5 blades, for a consolidation ratio of 10:1 and with a target utilization rate of 70%.

The first application virtualized was Tesco's new Real Time Sales (RTS), homegrown supply chain software that processes approximately 1,500 transactions per second, said Nick Folkes, Tesco's IT director for infrastructure and operations. Built on Microsoft BizTalk, RTS tracks "every basket of goods that goes through our tills," Folkes said. "When you buy a can of beans, [RTS] orders a new can of beans."

Less hardware for workload
By deploying RTS in a virtual rather than a physical environment, Tesco could reduce the amount of physical hardware dedicated to the application. Original design specs called for Tesco to deploy RTS on about 100 bare-metal servers, but the production deployment currently works on half as many virtual machines. Folkes explained that the efficiency has to do the high-availability and load-balancing capabilities in advanced virtualization platforms, which eliminated the need for clustering.

In the physical world, "you have one piece of tin doing all the work, while another piece of tin is sitting there doing absolutely nothing in case the first piece of tin falls over," Folkes said. In contrast to that 1:1 primary-to-failover model, Tesco has allotted just 15 blade servers from its pool of 150 servers to supply additional capacity in the case of failure.

The challenges of virtualizing RTS had little to do with technology, Folkes said. But "the challenge was to get the application providers to say, 'Yes, we'll support this,'" In the case of RTS, Microsoft sent over BizTalk engineers to examine the configuration before giving Tesco its blessing.Next on Tesco's to-do list is to extend virtualization to its disaster recovery site, which houses one physical box for every server in Tesco's production data center, standing by in case of disaster. Tesco will call on Citrix to help merge the production and disaster recovery facilities into "one homogeneous virtual environment," with servers at both facilities servicing workloads. "Ostensibly, you don't want to have metal sitting there doing nothing," Folkes said.Further out, Tesco will start exploring virtual desktops. "We have need to do IT projects with people we don't want on our corporate network," Folkes said. Providing contractors with a virtual desktop is a way to give them access to the resources they need, while enforcing a "logical break" on the network.

Citrix's latest coup against VMware?

The Tesco story is Citrix's second big customer case study within days. Last week, the company said that SAP SAP would virtualize some 500 Citrix XenApp servers onto Citrix XenServer. Last month Citrix said it would expand the capabilities of its free XenServer edition. That could make Citrix's flavor of virtualization more palatable for small-to-medium sized businesses, but some wonder whether it is on par with VMware. For Tesco's purposes, yes, said Folkes. He said he was initially concerned about using XenServer for disaster recovery and wondered whether its live-migration capabilities were sufficient. These days, though, "XenMotion is equivalent to the task we have at hand."If Citrix XenServer has shortcomings, they appear to be with fit and finish.

Bill Kleyman, the director of technology at World Wide Fittings Corp., a manufacturer of steel hydraulic tube and pipe fittings in Niles, Il., recently implemented XenServer on two hosts, and has been pleased with its performance, features and reliability. However, he characterized the alerting capabilities in XenServer's XenCenter management console as "really bad." "All it shows you is if the CPU is pegged and if you're using a lot of network [bandwidth] – that's it! It doesn't tell you if a physical host goes down" or if a virtual machine has failed. Kleyman said he had talked to Citrix about the problem, and that the virtualization provider said the problem will be fixed in a future release. On the bright side, Kleyman found that XenServer's HA capabilities work perfectly. When one XenServer host went down recently, HA rebooted the VMs on another host immediately, "and no one even noticed."