Thanks again for the good info and I’m glad that I read this when moving to vSphere as I’ve decided to stick with VMXNET2 (Enhanced) for the time being.

This post should be renamed…

More limitations of FT.

All our VM guests hosted on VI3 are being switched over to VMXNET2 for improved performance.

As we move guests to new vSphere clusters the vmware tools are being updated as well as the NIC types being changed. We’re considering updating the SCSI driver type too. Some guests still have buslogic and are being change to LSI Logic. I noticed now there are multiple choices, SAS, SCSI, etc…

For the few use cases where FT is needed or desired seems like it would be fine leaving the NIC at VMXNET Enhanced (VMXNET2).

Any thoughts on the performance advantages (or disatvantages) of the following SCSI controller types:
BusLogic Parallel
LSI Logic SAS
LSI Logic Parallel
VMware Paravirtual

Thanks for taking the time to share your knowledge. As a person responsible for the successful deployment of a virtual initiative I’m grateful to have resources like yours where I can get up to speed fast on the ups and downs of this technology.

While there’s no substitute for trial and error on the actual equipment, it’s very helpful to have a solid idea of where we’re going and how things will work.

Cheers!

VMXNET3 currently does not support VMDirectPath yet, so VMs using VMXNET3 are not tied to the physical host.

Virtual devices need enhancement to support FT and such enhancement does not exist in VMXNET3 yet, that’s why you cannot enable FT when the VM is using VMXNET3.

I think we’re all expecting many of the current limitations of FT to be relaxed in a future release, I would imagine this is when we’ll get separation between FT and VMXNET3. It could be an oversight in the current release, it could be that it wasn’t possible prior to GA date….

Scott V.

Although these drivers allow hypervisor bypass via VMDirectPath, that should not preclude their use with VMware FT. At least, that’s my humble opinion.

Thanks for the links (I’ve added them to the article) and for your great work!

Stu,

You are correct-in its current incarnation, VMware FT is incompatible with just about every other feature in VMware vSphere. I’m quite confident that VMware will address that in upcoming versions.

Brad,

I believe that the VMXNET3 issue is a bug; the VMware Communities thread to which I linked in the article has a response by a VMware employee that implies it is a known bug that will be addressed.

Igor,

Yes, of course–you could most certainly leverage PVSCSI and VMXNET3 on any virtual machines that will not be protected via VMware FT.

Thanks to all who commented!

It’s the same principle as not allowing VMotion of a VM with a CPU affinity set, or of a VM with it’s CD-ROM connected to an ISO image on the local VMFS.