Raw Device Mapping

What Does Raw Device Mapping Mean?

Raw device mapping (RDM) is a method of disk virtualization in VMware that allows virtual machines to use a storage logical unit number (LUN) device to be directly connected to a virtual machine in a storage area network (SAN). This direct connection can boost disk access performance in I/O-intensive operations.

Techopedia Explains Raw Device Mapping

Raw device mapping is one of two schemes that VMware servers can use to access storage. The other method is Virtual Machine File System (VMFS). VMware recommends VMFS for most applications.

Under RDM, a logical unit manager can be directly attached to a virtual machine. Connecting a device directly can improve performance, especially when virtual machines are clustered. RDM is suited to operations that depend on disk I/O, such as high performance computing.

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Margaret Rouse

Technology Expert

Margaret is an award-winning technical writer and teacher known for her ability to explain complex technical subjects to a non-technical business audience. Over the past twenty years, her IT definitions have been published by Que in an encyclopedia of technology terms and cited in articles by the New York Times, Time Magazine, USA Today, ZDNet, PC Magazine, and Discovery Magazine. She joined Techopedia in 2011. Margaret's idea of a fun day is helping IT and business professionals learn to speak each other’s highly specialized languages.

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