Informations about CPU- and RAM-HotPlug at VMs on VMware vSphere 5

Enable CPU-Hot Plug and RAM-Hot Add at Virtual machines on VMware vCenter 5
Update 12.02.2013 / Gabrie post in the comments a important extra info about Hot-Add and post the link to the blog from Duncan Epping it’s important to read this!!!
vSphere Virtual Machine Administration, Chapter 8 “Configuring Virtual Machines”, Section “Change CPU Hot Plug Settings in the … Client”, page 94.
Some conditions and requirements for CPU Hot Plug

  • If possible, use hardware version 8 virtual machines.
  • Hot-adding multicore virtual CPUs is supported only with hardware version 8 virtual machines.
  • Not all guest operating systems support CPU hot add.
  • To use the CPU hot-add feature with hardware version 7 virtual machines, set the Number of cores per socket to 1.
  • Adding CPU resources to a running virtual machine with CPU hot plug enabled disconnects and reconnects all USB passthrough devices connected to that virtual machine.
  • For Linux guest operating VMware Tools must be installed.
  • The virtual machine must powered off to configure he Hot CPU settings.
  • Hot remove of Memory is not supported.
  • Hot remove of CPU is not supported.

To enable new CPU after adding a new CPU. You can use this script:
Hot add cpu to supported Linux guestOS

# William Lam
# hot-add cpu to LINUX system using vSphere ESX(i) 4.0
# 08/09/2009
for CPU in $(ls /sys/devices/system/cpu/ | grep cpu | grep -v idle)
echo "Found cpu: "${CPU_DIR}" ..."
if [ -f "${CPU_STATE_FILE}" ]; then
STATE=$(cat "${CPU_STATE_FILE}" | grep 1)
if [ "${STATE}" == "1" ]; then
echo -e "t${CPU} already online"
echo -e "t${CPU} is new cpu, onlining cpu ..."
echo 1 > "${CPU_STATE_FILE}"
echo -e "t${CPU} already configured prior to hot-add"

Hot adding memory in Linux

ONLY for Suse Linux Enterprise Linux 11
Note: These instructions work for SLES OS. Other distributions may be different.
To enable acpi_memhotplug, run this command within the SLES virtual machine:

modprobe acpi_memhotplug

Using vSphere Client, edit the virtual machine settings to increase the memory assigned to the virtual machine. For more information, see Increasing the amount of memory assigned to a virtual machine (1004059).
Bring the memory online in /sys/devices/system/memory with the command:

echo online > /sys/devices/system/memory/memory[number]/state

Run this command to check the state of the memory, looking for memory that appears offline:

grep line /sys/devices/system/memory/*/state

If memory appears as offline, set it to online with the command:

echo online > /sys/devices/system/memory/memory[number]/state

Verify that you can see the extra memory with the command:

free -m

Expert Mode: PowerCLI

This Works when System is online, but need one “cold” start to enable this function.
Enable-MemHotAdd and Enable-vCpuHotAdd

Function Enable-MemHotAdd($vm){
$vmview = Get-vm $vm | Get-View
$vmConfigSpec = New-Object VMware.Vim.VirtualMachineConfigSpec
$extra = New-Object VMware.Vim.optionvalue
$vmConfigSpec.extraconfig += $extra
Function Enable-vCpuHotAdd($vm){
$vmview = Get-vm $vm | Get-View
$vmConfigSpec = New-Object VMware.Vim.VirtualMachineConfigSpec
$extra = New-Object VMware.Vim.optionvalue
$vmConfigSpec.extraconfig += $extra


Good information about hot-add cpu and memory can found here


Author: Sven-Jendrik Timmermann

Ich habe mich nie wirklich vorgestellt und das möchte ich mal nachholen 😉 Seit dem 20.4.2015 nun Selbständig. Familienvater von 3 Kindern, Tochter (3 Wochen), Sohn (3 1/2 Jahre), Stiefsohn (16 Jahre), Energie-Sparer, Optimist und großer Verfechter der Elektromobilität. Komme aus Nottensdorf, das liegt zwischen Buxtehude (Ja das gibt es wirklich!) und Stade, 30 Kilometer westlich von Hamburg Hier mal ein paar Themen in denen ich Euch helfen kann: #Architektur #Design #Sizing #Performance #Administration #Projektleitung#Projektplanung #Beschaffung #DataCore #VMware #VDI #Linux #Windows #Veeam #DataCenter#Hardware #SDDC #DR #Network #Office365 #DSGVO #GoBD#CloudGate365 #Lizenzen

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