vsphere-esxi-vcenter-server-55-storage-guide

Chapter 17 Raw Device MappingSnapshotsvMotionMakes it possible to use virtual machine snapshots on a mapped volume.Snapshots are not available when the RDM is used in physical compatibilitymode.Lets you migrate a virtual machine with vMotion. The mapping file acts as aproxy to allow vCenter Server to migrate the virtual machine by using thesame mechanism that exists for migrating virtual disk files.Figure 17‐2. vMotion of a Virtual Machine Using Raw Device MappingHost 1Host 2VM1VMotionVM2VMFS volumemapping fileaddressresolutionmapped deviceSAN ManagementAgentsN-Port ID Virtualization(NPIV)Makes it possible to run some SAN management agents inside a virtualmachine. Similarly, any software that needs to access a device by usinghardware-specific SCSI commands can be run in a virtual machine. This kindof software is called SCSI target-based software. When you use SANmanagement agents, select a physical compatibility mode for the RDM.Makes it possible to use the NPIV technology that allows a single FibreChannel HBA port to register with the Fibre Channel fabric using severalworldwide port names (WWPNs). This ability makes the HBA port appear asmultiple virtual ports, each having its own ID and virtual port name. Virtualmachines can then claim each of these virtual ports and use them for allRDM traffic.NOTE You can use NPIV only for virtual machines with RDM disks.VMware works with vendors of storage management software to ensure that their software functionscorrectly in environments that include ESXi. Some applications of this kind are:• SAN management software• Storage resource management (SRM) software• Snapshot softwareVMware, Inc. 157