ESX Virtualization

VMware ESXi, vSphere, VMware Backup, Hyper-V... how-to, videos....

Nakivo Backup and Replication - #1 Backup solution for Virtual, physical, cloud, NAS and SaaS

Menu
  • Certification
      • VCP-DCV vSphere 8
          • vcp2024-125.
        • Close
    • Close
  • VMware
    • Configuration Maximums
    • vSphere
      • vSphere 8.0
      • vSphere 7.0
      • vSphere 6.7
      • vSphere 6.5
      • vSphere 6.0
      • Close
    • VMworld
      • VMware EXPLORE 2024
      • VMware EXPLORE 2023
      • VMware EXPLORE 2022
      • VMworld 2019
      • VMworld 2018
      • VMworld 2017
      • VMworld 2016
      • VMworld 2015
      • VMworld 2014
      • VMworld 2013
      • VMworld 2012
      • VMworld 2011
      • Close
    • Close
  • Microsoft
    • Windows Server 2012
    • Windows Server 2016
    • Windows Server 2019
    • Close
  • Categories
    • Tips – VMware, Microsoft and General IT tips and definitions, What is this?, How this works?
    • Server Virtualization – VMware ESXi, ESXi Free Hypervizor, VMware vSphere Server Virtualization, VMware Cloud and Datacenter Virtualization
    • Backup – Virtualization Backup Solutions, VMware vSphere Backup and ESXi backup solutions.
    • Desktop Virtualization – Desktop Virtualization, VMware Workstation, VMware Fusion, VMware Horizon View, tips and tutorials
    • How To – ESXi Tutorials, IT and virtualization tutorials, VMware ESXi 4.x, ESXi 5.x and VMware vSphere. VMware Workstation and other IT tutorials.
    • Free – Free virtualization utilities, ESXi Free, Monitoring and free backup utilities for ESXi and Hyper-V. Free IT tools.
    • Videos – VMware Virtualization Videos, VMware ESXi Videos, ESXi 4.x, ESXi 5.x tips and videos.
    • Home Lab
    • Reviews – Virtualization Software and reviews, Disaster and backup recovery software reviews. Virtual infrastructure monitoring software review.
    • Close
  • Partners
    • NAKIVO
    • StarWind
    • Zerto
    • Xorux
    • Close
  • This Web
    • News
    • ESXi Lab
    • About
    • Advertise
    • Archives
    • Disclaimer
    • PDFs and Books
    • Close
  • Free
  • Privacy policy

What is VMware Hot-Add RAM and How to use it?

By Vladan SEGET | Last Updated: April 10, 2017

Shares

VMware Hot-Add RAM feature isn't new, but somehow we haven't covered it much just yet. So this post will explain What is VMware Hot-Add RAM and How to use it. The Hot-Add RAM goes hand in hand with Hot-Add CPU, but we'll cover that in a separate post.

Using hot-add/hot-plug you can add memory resources to virtual machines without any downtime. (not need to shut down). Actually, I tested this feature a while back on Hyper-V 2016 (pre-release), and it worked like a charm. Worth to note that VMware has this feature since a very very long time. (since 2009???).

Depending on which virtual hardware your particular VM has, what's the operating system of the VM (Yes, it matters), the feature works (or not) out of the box. The configuration of the feature has to be done VM shut down.

Where to configure VMware Hot-Add RAM?

I'll show you 4 different ways to configure this feature (and I'm sure there is a PowerCLI way as well).

vSphere Client

vSphere Client (Windows), which is phasing out. but still works on VM which uses up to VM hardware 11.

Newer virtual hardware isn't supported through this vSphere client. You must use vSphere web client or HTML5 client.

VMware Hot-Add RAM - vSphere Client

vSphere Web Client

The second way is vSphere Web client. You can use vSphere web client (Flash based) for configuration of all features of vSphere right now. This client has everything implemented. It is however still buggy, slow and dependent on Adobe Flash….

vSphere Web Client - Enable memory hot plug

vSphere HTML5 Client

This client is still at works, but this feature works well (tested). this is the new, upcoming, vSphere HTML5 based client. No plugins necessary, no Flash. A very cool way that will be the new management client for the whole vSphere infrastructure.

As you can see, the option is there….

VMware Hot-Add RAM - vSphere HTML5 Client

ESXi Host client (HTML5)

HTML5 host client allows management of single host only, but you can (if you run some rogue ESXi hosts or host not managed via vCenter server) enable this feature on the VM(s) if you like.

Here is the view….

VMware Hot-Add RAM - HTML 5 host client

What're the requirements for VMware Hot-Add RAM?

  • The virtual machine (VM) has to have a guest operating system that supports Memory hot-add functionality.
  • The virtual machine is using hardware version 7 or later.
  • VMware Tools is installed.

List of Guest OS which does support Hot-Add RAM

As you can see, “web” or “SMB” releases of Windows Server systems aren't supported… I don't have a full list of all supported Guest OS.

I know that RHEL is also supported. You should check VMware HCL. (choose Guest OS from the What are you looking for dropdown). The virtual hardware section under the Guest OS should read supported.

  • Windows Server 2003 32bit/64bit – (Standard and Enterprise)
  • Windows Server 2008 32bit (Standard, Enterprise and Datacenter)
  • Windows Server 2008 64bit (Standard, Enterprise and Datacenter)
  • Windows Server 2008 R2 (Standard, Enterprise and Datacenter)
  • Windows Server 2012 (Standard, Enterprise and Datacenter)
  • Windows Server 2012 R2 (Standard, Enterprise and Datacenter)
  • Windows Server 2016 Standard, (Standard, Datacenter) .. to be verified…

And in the real life?

VMware Hot-add RAM does not allow hot-reduce

Well, I've done a quick test in the lab on a Windows Server 2016 VM. While I could enable it and do an Hot-Add RAM to this VM without problems, the other way around it just not supported. You may be disappointed, but that's the way it is. You can grow up the RAM within the VM, but you can't “hot-reduce” the RAM. The VM has to be shut down and then only you can set the RAM to the level you like.

Wrap-up:

By default, virtual machines don’t support Hot Add (add RAM) and Hot Plug (add vCPU). You need to enable this capability on a per-VM basis in order to use it. Honestly, I don't think that if there is no possibility to hot-decrease RAM, then there won't be much use for this feature. Every time you want do decrease the RAM you'll have to shut down the VM and manually change the size of the vRAM. Well, possibly a PowerCLI script exists as a workaround?

If you're using this feature in your organization, please let us know in the comment section. I'm sure more users would be interested how it goes and which are the use cases.

More posts from ESX Virtualization:

  • Dedicated vSphere 6.5 Page
  • How to use VMware IOInsight – Free IO Testing Tool
  • Upgrade Windows Server 2012R2 AD to Server 2016
  • DISM ++ is Free Utility better than the command line version
  • What is VMware Orchestrated Restart?

Stay tuned through RSS, and social media channels (Twitter, FB, YouTube)

Shares
5/5 - (1 vote)

| Filed Under: Server Virtualization, Tips Tagged With: What is VMware Hot-Add RAM

About Vladan SEGET

This website is maintained by Vladan SEGET. Vladan is as an Independent consultant, professional blogger, vExpert x16, Veeam Vanguard x9, VCAP-DCA/DCD, ESX Virtualization site has started as a simple bookmarking site, but quickly found a large following of readers and subscribers.

Connect on: Facebook. Feel free to network via Twitter @vladan.

Comments

  1. Anonymous says

    April 11, 2017 at 5:52 pm

    Don’t forget about 3GB limit:
    https://kb.vmware.com/kb/2008405

  2. Nadeem Mushtaq says

    April 13, 2017 at 12:02 pm

    You may need to update List of Guest OS which does support Hot-Add RAM. Below are the extracts from vmware KB;

    “the Guest operating system support for CPU Hot Plug

    Windows: Windows Server 2012 (Standard and Datacenter Edition) and Windows Server 2008 Datacenter Edition support CPU hot add, but not CPU hot remove.

    Note: Windows Server 2008 Standard and Enterprise Editions do not support CPU hot add. ”

    Please see below link;

    https://kb.vmware.com/selfservice/microsites/search.do?language=en_US&cmd=displayKC&externalId=2020993

    • Vladan SEGET says

      April 13, 2017 at 2:12 pm

      I think that you should reread our post as we only invoke hot-add RAM feature, not the hot-add CPU. As such the comment is not relevant. But thanks for your reaction -:)…

  3. Christian holmqvist says

    April 16, 2017 at 12:11 pm

    Nice post as always. Im curious how hotAdd memory handles numanode in vsphere 6.5

Private Sponsors

Featured

  • Thinking about HCI? G2, an independent tech solutions peer review platform, has published its Winter 2023 Reports on Hyperconverged Infrastructure (HCI) Solutions.
  • Zerto: One Platform for Disaster Recovery, Backup & Cloud Mobility: Try FREE Hands-On Labs Today!
Click to Become a Sponsor

Most Recent

  • FREE version of StarWind VSAN vs Trial of Full version
  • Commvault’s Innovations at RSA Conference 2025 San Francisco
  • VMware ESXi FREE is FREE again!
  • Installation of StarWind VSAN Plugin for vSphere
  • Protect Mixed environments with Nakivo Physical Machine recovery (bare metal)
  • No more FREE licenses of VMware vSphere for vExperts – What’s your options?
  • Tails – Your Private OS on USB Stick
  • StarWind V2V Converter Now has CLI
  • Veeam VHR ISO v2 – 2025 Download and Install
  • Deployment OVA and Installation of Nakivo Backup and Replication for VMware

Get new posts by email:

 

 

 

 

Support us on Ko-Fi

 

 

Buy Me a Coffee at ko-fi.com

Sponsors

Free Trials

  • DC Scope for VMware vSphere – optimization, capacity planning, and cost management. Download FREE Trial Here.
  • Augmented Inline Deduplication, Altaro VM Backup v9 For #VMware and #Hyper-V – Grab your copy now download TRIAL.

VMware Engineer Jobs

VMware Engineer Jobs

YouTube

…

Find us on Facebook

ESX Virtualization

…

Copyright © 2025 ·Dynamik-Gen · Genesis Framework · Log in