What is the difference between RDM and VMDK?

VMDK—This is a file that appears as a hard drive to the guest operating system. Essentially, it is a virtual hard drive. RDM—This is also known as a pass-thru disk, and is a mapping file that acts as a proxy for a physical device such as a LUN.

What is an RDM in VMware?

Raw Device Mapping (RDM) is VMware’s virtualization technology that allows a virtual machine (VM) to access a logical unit number (LUN) directly.

Can you clone a VM with RDM?

VM snapshot functionality is available to RDM used in virtual compatibility mode. Irrespective of the compatibility mode, an RDM disk is a volume on the FlashArray. Therefore the steps for cloning a VM are the same for both modes.

Can you snapshot a VM with RDM?

Considerations and Limitations Cannot use snapshot feature with RDM in physical compatibility . Physical compatibility mode allows the virtual machine to manage its own, storage-based, snapshot or mirroring operations.

Can you vMotion VM with RDM?

Migrating virtual machines with RDMs can be performed in three ways: Warm migration (vMotion), with the virtual machine powered on. Cold migration, with the virtual machine powered off. Storage migration (Storage vMotion), with the virtual machine powered on.

What is RDM used for?

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.

What is the difference between RDM and VMFS?

Both formats enable you to access the virtual machine’s disk (VMDK), but they differ in approach to storage, and VMware recommends VMFS for the vast majority of VMs. With RDM, VMDK files are only pointers to a VM’s disk data, while on VMFS the files also hold the data. VMFS holds disk data from multiple VMs; RDM does not.

What is a VMFS file system?

VMware virtual machines comprise a set of files in typically one of two given formats: virtual machine file system ( VMFS) or raw device mapping ( RDM ). Both formats enable you to access the virtual machine’s disk (VMDK), but they differ in approach to storage, and VMware recommends VMFS for the vast majority of VMs.

What is the best file format for a VMware VM?

Source: courtesy of VMware. VMware virtual machines comprise a set of files in typically one of two given formats: virtual machine file system (VMFS) or raw device mapping (RDM). Both formats enable you to access the virtual machine’s disk (VMDK), but they differ in approach to storage, and VMware recommends VMFS for the vast majority of VMs.

What is the maximum number of LUNs in RDM?

With RDM, the VM directly connects to the storage area network (SAN) via a dedicated storage logical unit number (LUN). The total number of LUNs visible to an ESXi host is capped at 256, with the same LUNs visible across a whole cluster of up to 32 ESXi servers.

https://www.youtube.com/watch?v=uzCqc8XD5fI