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The Question of Database Virtualization -- Answered

By Kenneth Hess (Send Email)
Posted Jun 10, 2010


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If you believe that virtualization is limited to Web, application and a few other "lightweight" services, think again.

What's the latest myth you've bought into concerning virtualization? It probably has something to do with databases. Some database vendors want you to believe their database runs great only on dedicated physical hardware, and their expensive and proprietary solution is the only way to go. Virtualization vendors have proven otherwise. In fact, with the correct configuration, a virtualized database runs at or near native speeds.

Sure, there are solutions for MySQL running virtualized. Many people have done that. Microsoft's SQL Server runs virtualized. Microsoft will show you how. Other enterprise databases run well when virtualized, too. But the one you really want to know about is Oracle. Would you believe that Oracle is the best example of an enterprise database that runs flawlessly in a virtual environment? It is. Based on the Xen hypervisor, Oracle VM proves that it's time to rethink the "don't virtualize Oracle" myth. VMware and Citrix have also done their part for Oracle virtualization.

High Availability

What about Oracle RAC (Real Application Clusters) and other high availability solutions? The answer is that VMware provides a better solution by reducing complexity but maintaining high availability. There are three major benefits to VMware's high availability infrastructure solution:

  1. Lower-cost clustering and failover
  2. Ability to quickly restart Oracle instances
  3. Minimal interruption during maintenance and migration

Virtualization, specifically VMware virtualization, lowers the costs associated with clustering and failover through reduced hardware needs and lower complexity during hardware changes and testing. VMware's software makes it possible to decrease downtimes for maintenance and migration to minimal levels to meet those stringent service-level agreements (SLAs).

Performance

VMware tested single Oracle instances and RAC configurations and found that even very high throughput databases perform at 85 percent of native. Although the report didn't state it explicitly, performance should increase by placing the transaction logs and databases on raw SAN storage. Yes, you can map an entire physical LUN into a virtual machine. Yes, it does increase complexity, but the return is better performance.

For more detail, refer to the table below. This table shows data from VMware's benchmarks comparing native and virtual machine load profiles. As you can see, the virtual machines perform very well a under realistic load.

Metric Native VM
Throughput in business transactions per minute 293K 250K
Disk IOPS 71K 60K
Disk bandwidth 305MB/s 258MB/s
Network packet rate 12K/s receive
19K/s send
10K/s receive
17K/s send
Network bandwidth 25Mb/s receive
66Mb/s send
21Mb/s receive
56Mb/s send

Virtualization

Virtualization is ideal for rapid provisioning of Oracle instances via templates. Deploying a new Oracle instance from a virtual machine template takes minutes instead of days or weeks for traditional hardware and software delivery and setup. A virtual model also allows administrators to add capacity on an as-needed basis. Administrators may add memory, CPU, disk, network and additional instances with minimal downtime for users.

The speed of adding additional capacity with virtualization is by design and performed remotely. There's no need for any specialized on-site or data center access, no hardware to order, no systems to open and no chance of any accidental powering down of any other system.

Virtualization's adoption among database administrators, especially Oracle, is less than enthusiastic due to fears of I/O bottlenecks and support from the database system vendor. These fears should fade as VMware, Citrix and Oracle make their findings known to their customers who need to leverage virtualization to lower costs.

Oracle's customers, in particular, look to Oracle to "certify" solutions prior to their adoption because customers fear Oracle will not support a non-Oracle-blessed solution. According to VMware, Oracle doesn't certify such solutions, and virtualization on its platform should pose no significant support issues for the customer or the vendor.

Virtualization is a mature software and service offering on which you can rely. There is expertise available to you from VMware, Citrix, Oracle and other vendors to bring you a fully virtualized infrastructure. Databases are no exception. Virtualized database implementations also scale very well. VMware showed in its study that performance remained at 85 percent native for all CPU configurations.

Ken Hess is a freelance writer who writes on a variety of open source topics including Linux, databases, and virtualization. He is also the coauthor of Practical Virtualization Solutions, which is scheduled for publication in October 2009. You may reach him through his web site at http://www.kenhess.com.

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