Lets a VM use a physical LUN directly, through a mapping file stored on VMFS. Physical compatibility mode passes SCSI commands straight to the device, at the cost of VM snapshot support.
Also called Raw Device Mapping.
Read more: Broadcom TechDocs
In the Ultra Transcenders books
Each book explains RDM in context, with comparison tables and the common traps.
Terms in this definition
- Physical
Describes the concrete, real-world parts that put a logical architecture into effect.
- LUN
Logical unit number, the slot that identifies each data disk attached to a virtual machine. No two disks on the same VM can share one.
- VMFS
Clustered file system for block datastores, whether the storage is iSCSI, local or FC-attached. Unlike VMFS5, VMFS6 can use 4Kn devices and reclaims freed space by itself.
- SCSI
Small Computer System Interface, a standard for connecting disks. Hyper-V lets you hot-add or remove virtual SCSI disks on a running VM, and generation 2 VMs start up from them.
- snapshot
Captures a VM's disk state, power state, settings and, if requested, memory at a moment in time, using one delta disk per virtual disk. Snapshots should not be relied on as backups.