When IT managers store virtual machines on a storage area network, the typical option is VMware Virtual Machine File System (VMFS). For many applications, including file and print servers, web servers and enterprise resource planning applications, VMFS works fine.
But for processing-intensive applications such as SQL Server databases and e-mail, using VMFS can put too much overhead on the SAN. One approach used by the Navy Marine Corps Intranet is to use a technique known as Raw Device Mapping (RDM).
Jeff Smith, server manager for EDS, an HP company, which manages NMCI for the military, says Raw Device Mapping lets NMCI use the native file system on the storage area network to store the virtual machines.
“The best way to think about it is that RDMs are a way to more effectively use the space on the SAN and improve overall performance,” Smith says.
Smith says that although configuring RDMs is not especially hard, it does take someone who understands virtualization and the difference between RDM and VMFS. He says the need to use RDMs is one of the main reasons many agencies and other organizations have not yet moved to virtualize their sometimes numerous Microsoft Exchange servers.
“Most people just want to get virtualization to work and aren’t about to try virtualizing Exchange,” he says.
But that will change as more IT shops gain experience and their comfort level with virtualization technology grows. The potential cost savings and ease of management through virtualizing Exchange are too great for federal agencies to hold back, Smith expects.
Smith says virtualizing Exchange offers numerous benefits:
- Reduced server replenishment costs. NMCI says it will save on having to buy new servers every four years. At 150 servers, priced at roughly $10,000 per server, that’s at least $1.5 million in cost savings over four years.
- Central management. Now that the e-mail servers are virtualized, there’s less need to send people onsite to refresh or patch the servers. All standard maintenance can be done from a central location using VMware Virtual Center. With fewer servers, there’s also much less maintenance and testing required. Another benefit is that all the servers are HP 580 series so the IT managers don’t have to learn multiple hardware systems.
- Savings on facility space and resources. Between the Exchange servers, gateways and bridgehead servers, the mail operation for NMCI required nearly 200 servers. Virtualizing Exchange lets NMCI reduce its rack space, power and cooling requirements.