What Every DBA Should Know about Managing Databases in a Consolidated, Virtualized IT Infrastructure

A look at the key challenges DBAs may face with virtualization, plus best practices to address them.

by Scott Walz

Many businesses have moved to a virtualized environment—or are considering such a move for their IT infrastructure. Virtualization promises benefits such as reduced costs, increased agility, decreased energy consumption, and more efficient utilization of servers.

Industry research shows that deployment of virtualization technology is growing. For example, in the 2009 report Dataquest Insight: Virtualization Market Size Driven by Cost Reduction, Resource Utilization and Management Advantages, analyst firm Gartner Dataquest reports that worldwide virtualization software revenue increased 43 percent from 2008 to 2009.

The market will likely continue to grow as more organizations discover the benefits. However, the move to a consolidated, virtualized data center can provide significant challenges for IT professionals such as database administrators.

From a database management perspective, a virtualized IT infrastructure is significantly different from a traditional infrastructure with physical servers and storage devices, and there are pros and cons to moving to virtualization.

On the plus side, virtualization can lead to lower hardware costs, better and easier disaster recovery planning, and simplified scaling if more power is needed. On the negative side, virtualization can lead to increased software costs. Some database and OS software vendors have yet to offer virtualization-friendly licensing. Due to the ease of adding virtual hardware, more servers are created, which could lead to higher maintenance costs.

Following are some of the key challenges DBAs may face with virtualization, along with best practices for addressing them.

Storage Issues

One challenge of moving to a virtualized environment involves general storage issues; for example, segmenting disk I/O. Because the storage is now virtual, the database administrator loses a certain degree of control. A related issue is ensuring that data in a shared storage environment, especially one involving more than one company, is secure.

I sat down with Mark Monroe, president of Energetic Consulting and former director of strategic opportunities for cloud computing at Sun Microsystems. Mark spent a good part of the last decade working with Sun's marquee accounts that expressed interest in cloud computing and virtualization. Mark has developed strategies for Sun's expansion of its own public Platform-as-a-Service (PaaS) offering. He also managed the operational aspects of a 1,000-person IT division with a $200 million annual budget.

"People are concerned with data security when they're sharing devices with other customers," said Monroe. "In a more controlled case where it's shared storage within the same company, it might be less of a concern. But when you start sharing physical devices in a public cloud, data from Company A is mingled with Company B and Company C." That's a concern for many administrators.

Among the best practices for addressing these issues is leveraging the latest features of virtualization software and storage-area networks (SANs) that give DBAs the access and control they need in a virtualized environment, Monroe said.

He explained that the tools on SANs are good enough that administrators can get the access they need. He said the latest generation of virtualization software has a strong focus on performance and characteristics that make administrators comfortable with the new environment.

To address data security issues, DBAs need to be proactive in staying updated on the latest discussions about storage security. They should follow activities of groups such as the Storage Networking Industry Association (SNIA), which tap into security experts and vendors to stay abreast of security threats and issues. Also, they need to explore available technology for protecting storage resources in a virtualized environment.

"The technology is there to deal with these issues," Monroe said. "Stay involved, and you'll be able to alleviate the concerns you have."

Performance Levels

Another challenge of moving to a virtualized environment concerns performance levels. Virtualization involves the sharing of CPUs, and the ramifications of that include possible performance issues for the DBA. How might these performance issues affect day-to-day operations? That has long been a concern of companies considering a move to virtualization.

Organizations adopting virtualization can easily encounter virtual machine sprawl, where numerous virtual machines affect database performance levels. "There's always a concern of runaway processes or virtual machines overwhelming the physical resources and making everyone else suffer," Monroe said.

There are ways to throttle virtual machines using the latest virtualization software. Companies can set up their machines so that they only have access to 25 percent of CPU space, for example. If they set parameters carefully and give virtual machines only limited use of memory and CPU access, they can address performance issues.

"Even if there's a process running inside that thinks it's at 100 percent, it's only taking up one of four cycles," Monroe said.

Performance tuning of databases is especially critical in a virtualized environment, and virtualization might be why more recently performance has become such a challenge for companies. DBAs need to stay on top of this, and explore tools on the market that help ensure high performance levels.

Governance/Compliance/Security

Providing effective governance, compliance and information security in a virtualized environment is yet another challenge for administrators. Although physical servers are the responsibility of IT or data center managers, in a virtualized environment there may be uncertainty about who is responsible for security management.

DBAs need to ensure that databases are secure even with the new layer of technology virtualization brings. Security management includes keeping up with the latest patches. Managers need to be as rigorous about governance in the virtualized environment as they are with physical servers. That includes ensuring that there's proper security, adhering to regulatory compliance policies, and guarding against virtual machine sprawl.

Monroe said VM sprawl in particular was always a worry when he worked at Sun. "We already had physical server sprawl, and we were very concerned about virtual server sprawl," he explained. "With virtual machines, it's so easy to go to a manager and say 'I'd like another virtual machine.' You might need it again, so you leave it running. In a matter of months you could have tens of thousands of virtual machine husks in your virtual space, and no one knows what they're for."

A governance program would oversee the creation and destruction and management of virtual machines to avoid sprawl and the possible negative impact on database performance.

Cultural Concerns

Finally, there are cultural issues to address. Moving to a virtualized environment presents changes in how databases are managed and how they're accessed. Departments may lose some of the autonomy they've had with the traditional data center environment and dedicated servers.

In many cases, virtual machines will be shared by multiple groups of users accustomed to having their own, dedicated servers.

"There's a certain amount of server hugging, where people say, 'This is my machine, I know where it is and I'm assured I can get my hands on it,'" Monroe said. "We're moving people to a virtual world where we say we'll decide where the virtual machine physically lives. We the IT organization are managing a set of assets that are virtualized, and we will decide where data is stored on a SAN. Some people get real nervous with that."

Often what it takes to overcome the cultural barriers is to offer database users compelling reasons for moving to a virtualized environment. For example, virtualization can result in huge cost reductions or faster time to server implementation.

"There has to be some dimension to get them to move off," Monroe said. For example, managers at Sun created an Agile Computing Environment (ACE), where computers were a set of standardized hardware and virtualization software on physical boxes. Business users were presented with the benefits of virtualization such as fast turnaround time for server implementations—as quickly as one week in some cases.

"Most of them would say 'We can use the ACE environment,'" Monroe said. "We gave them a compelling reason."

Many organizations are finding compelling reasons to adopt virtualization or expand their virtualized environment -- and this can present some challenges for database administrators. However, with the right approach to addressing these hurdles, DBAs can help their organizations ensure a successful virtualization project.

Scott Walz has more than 15 years of experience in the area of database development and currently serves as the senior director of product management for Embarcadero Technologies. You can contact the author at scott.walz@embarcadero.com