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Tech TopX: Increasing CVM Memory in AOS 5.1

  • 20 September 2017
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Tech TopX: Increasing CVM Memory in AOS 5.1
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So you're on a version of AOS prior to 5.1 and you're thinking of upgrading to get some of the new features. Well, there's some important memory changes with respect to the CVM that need to be considered before upgrading.

My name is Matt Gauch, and if you aren't already aware, the CVM is essential to the operation of the Nutanix environment. As we add more features, it's critical to ensure that the CVM has enough resources to support those features. Everything is pretty well documented. I'm going to show you exactly what to expect when upgrading to AOS 5.1. With that, let's jump right in.



First, I'd like to start by covering the current memory requirements for your CVMs in both 5.0 and 5.1. Again, just log into the Nutanix support portal. In the search bar, if you just type in, "CVM memory," it's going to pull up a list of links, and what you can see from here is which version of AOS applies to, and what the configurations are for the feature. If you go ahead and click this first link that'll pop up, and then we'll go to the parent topic by clicking up here, you're going to see a list of the CVM memory configurations as they currently stand on 5.1.1.3. This is broken down by machine type based on CPU, so you'll see a list of the G5/Broadwell, and then below, you'll see the G4 machine, so on and so forth.

Just keep in mind that these numbers are all going to be 4GB higher than what was previously accepted for the CVM. What I'm going to do is copy this link and show you the memory requirements for 5.0.3.2 just to notate the difference. So you'll see in 5.0.3.2, we'll look at the same exact chart, the differences are all by 4GB, so you got 16GB, 24GB, 24GB, and 32GB. You got 20GB, 28GB, 28GB, and 32GB. We won't go higher than 32GB, just something to keep in mind when you guys are upgrading to 5.1. So after you've notated the memory requirements, if you are coming from AOS 5.0 or 4.x in going to 5.1, it's important to keep in mind that the memory is going to be adjusted by 4GB.

Again, going back to Portal, if you go to the downloads up at the top, click on "AOS", and choose "5.1.1.3," and now you'd agree and download the file. On this page, though, you're going to see these release notes. In the release notes, it's going to point out these memory changes in detail. So right here, it says, "There's a one time memory increase requirement for customers upgrading from 4.7 or 5.0 versions. It's required for each Controller VM, and it's because of the increased number of services that we offer and support in the 5.1 family."

If you're running vCenter, there's a required script that you need to download and run on your host. Next, I'm going to cover that script. Should be in KB 4332, so again, if you just go here, click on "documentation," "knowledge base," click the search, just filter out. So you're going to see this, "get_vCenter_info" script. What the script allows us to do is obtain your vCenter credentials, and it gives us permissions to alter CVM memory during the upgrade. So the CVM will be powered off, we'll increase the memory accordingly, and then it'll be powered back on.

So in the KB, as you scroll down below the solution, you're going to see the download link. What I normally do is just right click, copy link address, and then I'll move on over to my PuTTy session for one of my CVMs. You can do this on any one CVM in the cluster. You just do a wget on that file. It's going to download that script. You can verify where it is by just running an ls to get_vcenter_info script. So chmod it, is to get, tap it out, and run it.

It's going to prompt you for the number of vCenter servers. Throw in the IP address of your vCenter server. Put in a user name and then your password. Then it's going to ask you if you want to proceed, then it'll say "success," and you're ready to go ahead and do the AOS upgrade on your ESXi cluster. Once that's done, you'll notice that all the CVMs will have 4GB additional memory. This change will only take place if the CVM memory is less than 32GB. We won't increase the memory beyond 32GB.

The next thing I want to discuss today is the ability to now change CVM memory through Prism. So if you want to go ahead and log into prism, you can click on the gear in the upper right corner, scroll down to "configure CVM." This will allow you to select a predetermined memory increase for your cluster. You pick one of the three options you'll see. If you're already at a current version, the options will be less. Hit "apply" and that'll go ahead and perform a rolling reboot of the CVMs. Again, if this in the ESXi cluster, you'll have to run the script I previously mentioned.

So the final thing I wanted to mention is 5.1 now takes into account cluster expansion. So when you go to expand your cluster, previously if you had, say, your CVMs running at 24GB to account for a feature that was enabled such as deduplication, it would bring the CVM into the cluster at whatever current configuration it had, which could theoretically disable dedupe, because it would no longer be supported if one of the CVMs didn't have the right amount of memory.

The new way it's done is cluster expansion will look at the memory in a system and whatever features are enabled, and it will ensure that whichever CVM you're bringing into the cluster has the right amount of memory to prevent one of the features inadvertently being disabled. So once you have your CVM ready, you just click through the cluster expansion wizard and you no longer have to worry about adjusting memory after the fact.

Hopefully that wasn't too bad. Please hit the subscribe link below so you can stay up to date on the latest content. Speaking of content, if there's anything you'd like to see, just let us know. As always, thank you for tuning in to Tech TopX.

Resource links
5.1.1.3 CVM Memory configurations
5.1.1.3 Release Notes
KB 4332 for vCenter script

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