Merry Christmas

Just a short note to say merry christmas and best wishes for the new year to you and your family, thanks for visiting.



Virtualization VMWare

Cold migration in VMWare – What is it?

So the topic of what is a cold migration (in VMWare vmotion speak) came up in a conference call today with a customer.

It is a migration strategy when there are CPU compatibility constraints  between certain revisions of CPUs, it basically means there is no path to use v-motion as such so will associated outages.
When does it occur?

As mentioned, cold migration is a strategy or a decision to migrate virtual machines between different revisions of CPU (whether it be manufacturer or models). An example might be going from an AMD chipset to an Intel chip.  There are cases that going from a same vendor CPU requires an outage so cold migration would be an option.  More information on what to check, how to check can be found here

What happens? 

Quite simply, the virtual machine is powered off on the source host and powered on, so there is an outage but as long as both ESXi servers have visibility to the same shared storage, then cold migration can be very fast and the virtual machine downtime kept to a minimum.
The difference to vMotion

Biggest difference, vMotion is (typically) performed without any downtime on the virtual machine where as cold migration requires an outage to power down and power up the virtual machine on the destination host.

Another notable difference it happens at a management network layer and not the VMKernel layer (which vMotion uses)

That is cold migration in a nutshell!

Virtualization VMWare

VCP 510 exam – My thoughts

Having recently sat the VCP 5 exam, I thought I would offer some tips and study advice.  Overall, there are 85 multi-choice questions and you have 90 mins to complete and their is a lot more focus on new features, troubleshooting, and configuring than previous versions of the exam which was usually based around limitations and maximums.




  • VMKernel securing – how (and where) to do it.
  • Load balancing policies
  • Path Selection policies – Quite a few questions on these.
  • Traffic shaping
  • VDS – Lots on this topic. What features are unique to VDS and what aren’t,
  • Promiscuous mode vs forged transmits – About 2 questions involving these
  • Restarting management network – how to do it in vSphere 5
  • Securing your host – turning off ssh etc.
  • Uplinks – what are they and what do they do. Relationship with vSwitches
  • CNA – Question around image profiles and driver certification
  • ISCSI and implications of changing certain parameters such as CHAP


  • New features: VMFS3 vs VMFS 5, migration to VMFS5 – what changes and what doesn’t. Maximum file size supported
  • VSA – How to configure. Valid states of a VSA
  • RDM – Physical compatibility vs Virtual
  • Storage Profiles – Learn what it does.
  • VMKernel interation with storage array, what the array does and what the kernel does
  • VAAI – Benefits of VAAI and what the supported array can do.
  • Trouble shooting storage performance – What counters to look at

Advanced Features

  • HA – What it does.
  • FT – Why you would use it – use cases
  • DRS – Ports for DRS and HA
  • vMotion/EVC – Where to configure and requirements around CPU. NPIV and vMotion compatibility
  • Resource Pools, shares, limits and reservations – Lots of questions around these, learn what increasing and decreasing each element does and the effect.
  • Performance tuning and troubleshooting – They give you line graphs and ask you to understand and diagnose the issue, scenario based troubleshooting. (I.e Image shows error, what is the cause), ESXtop
  • Memory conservation – TPS vs ballooning
  • Upgrading from ESX3 to ESXi5 – One question on this, basically you can’t do it.
  • Upgrading from ESX4 to ESXi5 – rules, methods and things you need to look out for.
  • How to back up a ESXi host before upgrading
  • Understanding alarm warnings and alerts and how to configure
  • vApps and IP allocations, and what objects they contain.
  • Log file configuration. Increasing etc
  • vCenter Server – What extra capabilities does it give you over managing a host directly.
  • Auto Deploy – Learn Image profiles and how to use.
  • VSA – Quite a few on this, how to upgrade from earlier version was one question
  • Modifying Users and permissions and the impacts

Hope that helps.