Yellow Bricks

by Duncan Epping

ft

vSphere FT and vVols/SPBM an unsupported config? Why?

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I was pointed out by a customer (thanks Johan), that vSphere FT is not supported when using SPBM on non-vSAN based storage systems. You may wonder why this is, at least I did wonder. I figured it would be a testing constraint of some sort, but after emailing product management, engineering, and our quality engineering team I now understand why it is. Now before I explain it, the constraint is documented here, let me quote the section for you:

Virtual Volume datastores.
Storage-based policy management. Storage policies are supported for vSAN storage.

So why is this and why would vSAN be supported as that also uses SPBM? Well the difference is in the implementation. For vVols there’s a dependency on vCenter Server to be available when creating new VMs. This is essentially what happens when an FT instance needs to be restarted. We will need to associate an SPBM policy with it and we can only retrieve it via vCenter Server. With vSAN, FT/HA can also retrieve the needed info via the ESXi host. This is why FT and vSAN are a supported configuration, and vVols and FT, unfortunately, is not at the moment. Hopefully, though, this will change in the future. (Yes, I filed a feature request before anyone asks.)

Changing advanced vSphere FT related settings, is that supported?

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This week I received a question around changing the values for vSphere FT related advanced settings. This customer is working on an environment where uptime is key. Of course the application layer is one side, but they also want to have additional availability from an infrastructure perspective. Which means vSphere HA and vSphere FT are key.

They have various VMs they need to enable FT on, these are vSMP VMs (meaning in this case dual CPU). Right now each host is limited to 4 FT VMs and at most 8 vCPUs, this is being controlled by two advanced settings called “das.maxftvmsperhost” and “das.maxFtVCpusPerHost”. The values for these are, obviously, 4 and 8. The question was: can I edit these and still have a supported configuration? Also, why 4 and 8?

I spoke to the product team about this and the answer is: yes, you can safely edit these. These values were set based on typical bandwidth and resource constraints customers have. An FT VM easily consumes between 1-3Gbps of bandwidth, meaning that if you dedicate a 10Gbps link to it you will fit roughly 4 VMs. I say roughly as of course the workload matters: CPU, Memory and IO pattern.

If you have a 40Gbps NIC, and you have plenty of cores and memory you could increase those max numbers for FT VMs per host and FT vCPUs. However, it must be noted that if you run in to problems VMware GSS may request you to revert back to the default just to ensure the issues that occur aren’t due to this change as VMware tests with the default values.

UPDATE to this content can be found here: https://www.yellow-bricks.com/2022/11/18/can-you-exceed-the-number-of-ft-enabled-vcpus-per-host-or-number-of-ft-enabled-vcpus-per-vm/

SMP-FT support for Virtual SAN ROBO configurations

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When we announced Virtual SAN 2-node ROBO configurations at VMworld we received a lot of great feedback and responses. A lot of people asked if SMP-FT was supported in that configuration. Apparently many of the customers using ROBO still have legacy applications which can use some form of extra protection against a host failure etc. The Virtual SAN team had not anticipated this and had not tested this explicit scenario unfortunately so our response had to be: not supported today.

We took the feedback to the engineering and QA team and these guys managed to do full end-to-end tests for SMP-FT on 2-node Virtual SAN ROBO configurations. Proud to announce that as of today this is now fully supported with Virtual SAN 6.1! I want to point out that still all SMP-FT requirements do apply, which means 10GbE for SMPT-FT! Nevertheless, if you have the need to provide that extra level of availability for certain workloads, now you can!

vSphere Availability Survey, please help out!

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Just received the below from the vSphere Availability team. It takes a couple of minutes to fill out and it helps the vSphere Availability team to set priorities correctly for upcoming releases, yes indeed based on your answers!

— copy / paste —

The Availability team (that brings to you products such as vSphere HA, FT etc.) would like to get your input on how you use our products today and your projected needs. The survey has mainly multiple choice questions, and will take 10-15 minutes to complete. Your feedback is invaluable in helping us tailor our development efforts towards valuable enhancements. So, thank you!

Here’s the link to the survey: http://tinyurl.com/vmwavailability

VMware Availability Survey

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I just received the following… If you have some spare time on your hands please fill out this survey, it would be much appreciated.

We are hard at work building our future products to better meet your needs. As part of this process we are developing a 3-year strategy for the VMware Business Continuity offerings, and are seeking your input to best align our strategy with your business objectives.

Please bring your voice to the table – if you have a few minutes today, would you please click on the link below and share your insights on the VMware Business Continuity road map. Answer as few or many of the questions as you’d like.

https://vmware.allegiancetech.com/cgi-bin/qwebcorporate.dll?idx=6KGA9Q