Which Virtual Hardware Configurations Allow Snapshots?

ABD.

Snapshots in vSphere allow you to capture the state of a virtual machine (VM) at a specific point in time. With snapshots, you can preserve a VM's state, including its disks, memory, and virtual hardware configuration.

However, not all virtual hardware configurations allow snapshots. Here are the three configurations that do:

1. 16+ vCPU: Virtual machines that have 16 or more virtual CPUs (vCPUs) can take snapshots. This is because vSphere requires more resources to take a snapshot of a VM with a large number of vCPUs, and it may impact performance during the snapshot process.

2. Full memory reservation: Virtual machines that have a full memory reservation can take snapshots. A full memory reservation ensures that the VM's memory is always available, and that vSphere does not need to swap out memory pages to the disk during the snapshot process. This can help ensure that the VM's state is captured accurately and without any performance impact.

3. Bus sharing: Virtual machines that use bus sharing can take snapshots. Bus sharing allows multiple virtual machines to share a virtual SCSI bus, which can help optimize storage performance. When a VM takes a snapshot with bus sharing, vSphere captures the state of the shared SCSI bus, including any attached disks.

Virtual Mode RDMs and Physical Mode RDMs do not allow snapshots. Raw Device Mapping (RDM) is a technique that allows a virtual machine to access a physical disk directly, rather than using a virtual disk file. Virtual Mode RDMs use a file in the VMFS file system to represent the RDM mapping, while Physical Mode RDMs use a raw LUN mapping. However, neither mode allows snapshots because they bypass the virtual disk layer of vSphere, which is necessary for taking a snapshot.

In summary, the three virtual hardware configurations that allow snapshots in vSphere are 16+ vCPU, full memory reservation, and bus sharing.