Until recently, IT shops and vendors alike agreed that it was a bad idea to virtualize high throughput applications such as SQL Server databases or Exchange Server.
While this may still hold true in extreme cases, running these applications in virtual machines may work fine for many workloads, according to experts.
The assumption has been that that database and messaging server workloads are not suited for virtualization in that they are transactional, so by extension, their workloads require more memory and CPU access, but such applications function just fine as a virtual machine, said David Payne, CTO at Xcedex Inc., a Plymouth, Minn., integrator and virtualization expert.
Today, IT managers and database administrators may be counting on virtualization as a way to cope with greater workloads as more servers are added. In the database world, for example, a SearchSQLServer.com survey of 372 database administrators and IT managers shows that 26% of respondents plan to manage their growing servers by running them in virtual machines.
Another 36% plan to manage the servers through server consolidation. About 22% will look at physical server consolidation for greater efficiencies. About 10% plan to use more policy automation. And 6% expect to hire more database administrators.
In our department there are 12 virtualized SQL Servers that store a variety of data, said Janssen Jones, associate director of auxiliary information technology infrastructure at Indiana University located in Bloomington, Ind.
"We develop a lot of applications with a Web front end and a SQL Server back end and have virtualized SQL in development, test and production environments," he said. "These servers host data for applications such as student housing, dining and parking."
Jones said conventional wisdom was not to virtualize databases on Microsoft's Virtual Server, but rather on VMware Inc.'s ESX. "We decided to try it on [Microsoft's] Hyper-V to see what happens because we had more pain from trying to maintain the physical boxes," he said.
The I/O did not suffer and there was no decrease in performance, he said. "When we saw that we virtualized more and more and now we are 80% to 90% virtualized."
Still, the idea of virtualizing SQL Server and Exchange in production environments doesn't sit well with everyone. Sumeeth Evans is the IT director at Collegiate Housing Services in Indianapolis. He said that in the case of Exchange Server, it may make more sense for his organization to run a machine with the Local Continuous Replication Exchange server role in a virtualized environment.
"We are looking at this," Evans said. But performance remains a concern at the student housing service, which has a lot of e-commerce applications. There are certain times of the month, when students pay rent for example, when high server traffic may not make virtualization a good value, he said.
Where to virtualize applicationsPayne said database servers that tend to do well in virtual environments are the ones that house infrastructure support systems, such as those used for saving configurations. "It's the workhorse SQL Servers that have the problems," Payne said. "[It's not appropriate] when you are consuming greater than two to four CPUs of processing power and you need enormous memory for tens of thousands of transactions."
Exchange Server works well in a virtual machine but can cause problems when scaling up within a limited number of servers. "It's not as bad if you scale up and split your mailboxes," Payne said. He recommends that IT shops adjust their deployment to a scale out method to virtualize these applications.