Yellow Bricks

by Duncan Epping

BC-DR

How to simplify vSAN Support!

· ·

Last week I presented at the Tech Support Summit in Cork with Cormac. Our session was about the evolution of vSAN, where are we today but more importantly which directly will we be going. One thing that struck me when I discussed vSAN Support Insight, the solution we announced not to long ago, is that not too many people seemed to understand the benefit. When you have vSAN and you enable CEIP (Customer Experience Improvement Program) then you have a phone home solution for your vSphere and vSAN environment automatically. What this brings is fairly simple to explain: less frustration! Why? Well the support team will have, when you provide them your vCenter UUID, instant access to all of the metadata of your environment. What does that mean? Well the configuration for instance, the performance data, logs, health check details etc. This will allow them to instantly get a good understanding of what your environment looks like, without the need for you as a customer to upload your logs etc.

At the event I demoed the Support Insight interface, which is what the Support Team has available, and a lot of customers afterwards said: now I see the benefit of enabling this, I will do this for sure when I get back to the office. So I figured I would take the demo, do a voice over and release it to the public. We need more people to join the customer experience improvement program, so watch the video to see what this gives the support team. Note by the way that everything is anonymized, without you providing a UUID it is not possible to correlate the data to a customer. Even when you provide a UUID the support team can only see the host, vm, policy and portgroup (etc) names when you provide them with what is called an obfuscation map (key). Anyway, watch the demo and join now!

22 / 23 May 2018 – VMware Technical Support Summit

· ·

A while back I was asked if I could present at the VMware Technical Support Summit and last week I received the agenda. I forgot to blog about it so I figured I would share it with everyone. I was supposed to go to this event last year but I had a clash in my calendar unfortunately. At this event organized by our support team you will have the ability to sit in some extreme deep dive sessions. Below you can find the agenda, and also here’s the registration link if you are interested! Note that Joe Baguley will be doing a keynote, and Cormac Hogan and I will be doing a session on vSAN futures!

vSphere HA Restart Priority

· ·

I’ve seen more and more questions popping up about vSphere HA Restart Priority lately. I figured I would write something about it. I already did in this post about what’s new in vSphere 6.5 and I did so in the Stretched Cluster guide. It has always been possible to set a restart priority for VMs, but pre-vSphere 6.5 this priority simply referred to the scheduling of the restart of the VM after a failure. Each host in a cluster can restart 32 VMs at the same time, so you can imagine that if the restart priority is only about VM restarts that it doesn’t really add a lot of value. (Simply because we can schedule many at the same time, and the priority would as such have no effect.)

As of vSphere 6.5 we have the ability to specify the priority and also specify when HA should continue with the next batch. Especially this last part is important, as this allows you to specify that we start with the next priority level when:

  1. Resources are allocated (default)
  2. VMs are powered on
  3. Guest heartbeat is detected
  4. App heartbeat is detected

I think these are mostly self-explanatory, note though the “resources are allocated” means that a target host for restart has been found by the master. So this happens within milliseconds. Very similar for VMs are powered on, this also says nothing about when a VM is available. This literally is “power on”. In some cases it could take 10-20 seconds for a VM to be fully booted and the apps to be available, in other cases it may take minutes… It all depends on the services that will need to be started within the VM. So if it is important for the “service provided” by the VM to be available before starting the next batch then option 3 or 4 would be your best pick. Note that with option 4 you will need to have VM/Application Monitoring and defined within the VM. Now when you have made your choice around when to start the next batch you can simply start adding VMs to a specific level.

Instead of the 3 standard restart “buckets” you now have 5: Highest, High, Medium, Low, Lowest. Why these funny names? Well that was done in order to stay backwards compatible with vSphere 6 / 5 etc. By default all VMs will have the “medium” restart priority, and no it won’t make any difference if you change all of them to high. Simply because the restart priority is about the priority between VMs, it doesn’t change the host response times etc. In other words, changing the restart priority only makes sense when you have VMs at different levels, and usually will only make a big difference when you also change the option “Start next priority VMs when”.

So where do you change this? Well that is pretty straight forward:

  • Click on your HA cluster and then the “Configure” Tab
  • Click on “VM Overrides” and then click “Add”
  • Click on the green plus sign and select the VMs you would like to give a higher, or lower priority
  • Then select the new priority and specify when the next batch should start

And if you are wondering, yes the restart priority also applies when vCenter is not available. So you can use it even to ensure vCenter, AD and DNS are booted up first. All of this info is stored in the cluster configuration data. You can examine this on the commandline by the way by typing the following:

/opt/vmware/fdm/fdm/prettyPrint.sh clusterconfig

Note that the outcome is usually pretty big, so you will have to scroll through it to find what you need, if you do a search on “restartPriority” then you should be able to find it the VMs for which you changed the priority. Pretty cool right?!

Oh, if you didn’t know yet… Frank, Niels and I are actively updating the vSphere Clustering Deep Dive. Hopefully we will have something out “soon”, as in around VMworld.

Changing advanced vSphere FT related settings, is that supported?

· ·

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/

Happy 10th Birthday Yellow-Bricks.com

· ·

Just wanted to share with all of you the fact that this week marks the 10th anniversary of Yellow-Bricks.com. Crazy thinking back about how it all started, and what it turned in to. Thanks everyone for taking the time to read and comment on many of the articles over the years. Those wondering what’s next, what to expect in the upcoming year? Well definitely an update to the vSAN Essentials book released yesterday, but also an update to probably one of the best sold VMware related books: