Can external legacy storage be accessed via Nutanix AHV or ESXi?

Hello vkumarjr,

Thank you for your reply, but let me clarify my question.

When I used the term “access” to an external device, I meant some type of pass through of the IO to a specific VM (through a hypervisor). This VM would need to have the proper device drivers installed within the VM’s operating system to support and manage the external device.

I was not asking for Nutanix to “manage” the external device, or even know anything about it.

The next sub-question would be whether the IO to this external device could go through a host controller that could be used for other purposes? This would mean that their could be co-mingled devices attached to this controllers, some managed by Nutanix, some by the “special” VM.  This co-mingling, especially without some SR-IOV-like support, opens up significant risk, as the controller is being shared in some form between Nutanix and the special VM.  If one software stack issues some form of “device reset”, it could cause errors and IO corruption with IO in progress from the “other” software stack.

OK.  So for robustness … the “special” host IO controller for this external storage device would need to be exclusively reserved and assigned to this “special” VM (through its hypervisor), and conversely, Nutanix software may need to be configured to ignore this “special” controller for its own use … ie, don’t try to “discover” devices on this controller.

So with an “exclusive” controller, this question about allowing connection to an external device, degenerates into a form of a generic pass-through capability, possibly with an exclusion list for Nutanix to ignore the controller.

This pass-through capability can be a very useful mechanism to allow for use of various “accelerator” or “special” devices for specific interested customers, before these “special” devices are broadly needed by the general Nutanix customer population. If these “special” devices become popular, Nutanix can make the business decision to offer some higher level of support or functionality. 

There are many examples of such “special” PCIe devices; GPUs from Nvidia, AMD, and now Intel, various AI-related compute engines for machine learning, custom FPGAs and ASIC accelerators, many of which have been used in the high-performance financial trading industry.  As the industry moves forward to 100 gbit and faster network connections, there is an increased need for additional “offloads” of encryption, checksumming, and other functions because the general purpose Intel/AMD CPUs can no longer process the data at line rate.

So the main question is NOT for Nutanix to support some low-volume controller (which opens up many risks), but to allow for a form of pass-through to a designated hypervisor and specially assigned VM.  This also assumes that the hypervisor knows how to pass through the host controller management to the specific VM. This may or may not mean that AHV can be used for this hypervisor.

The benefit for the customer, as stated as a goal of Nutanix, is offering customer “choice”.  In this case, the choice of using some special device, not-managed by Nutanix.

Perhaps this “special” Nutanix node is one of the new compute-only nodes, with no local Nutanix supported local storage … that has a “special” host controller being passed through to a “special” VM.

A concrete example for large legacy customers, would be to allow access to some form of cold archive system (often robotic tape libraries) that contain hundreds of petabytes of information.  Asking a customer to migrate this cold archive data to Nutanix converged storage is unrealistic, and cost-prohibitive.

Again … let me stress … at the initial phases … this is a host controller pass-through issue. I am not asking that the Nutanix software “manage” the host controller, other than a pass through to the hypervisor, and ultimately the VM.

Thank you for your help and feedback.

Regards,

db808

Thank you Vignesh,

Unfortunately, this is not the answer that I was looking for.  Please relay this information to the product roadmap people.  I can summarize it as two major points.

Customers are already using and have investments in expensive “devices” today that they would like to access from the Nutanix environment.  These devices fall into two broad classifications:

1. External Devices using a readily available controller with support already in Linux and Windows.  Examples would be fibre channel controllers, SAS controllers, USB3 controllers. Types of external devices using these controllers are typically forms of disk and tape storage. Customers already have systems, sometimes even virtualized systems that are connected and using these external devices. It would be valuable to support some form of “raw” connection to these external devices, with the management done by the drivers in the VM.  As an analogy, think of an external iSCSI device, which could be directly accessed by a VM today.  Nutanix is not involved in managing the external iSCSI device.  It is handled as a socket connection to a remote endpoint.  It would be useful to access such external devices also via fibre channel, and perhaps SAS.
2. “Special” interface and/or accelerator controller, such as a GPU, ASIC, FPGA, or other PCIe controller.  This would need some form of controller passthrough to the hypervisor and VM. 

Without having a workaround for item #1 .. the external disk or tape archive over fibre channel or SAS, Nutanix is forcing the customer to build/buy/create some form of gateway system that can wrap the external device’s access into something that can be accessed via Ethernet/TCP.  This can be a non-trivial undertaking … and offers a significant impediment to the use of Nutanix HCI systems.  Effectively, Nutanix is in itself its own “silo” with limited access to important (and expensive) external devices using fibre channel and/or SAS connections.

Thank you for your feedback,

Dave B

db808