Feb 02 2015

vSphere 6.0 blog – Fault Tolerance


This is the second part of the new vSphere 6.0 improvements and or new features blog series. The first part covered the vMotion improvements and can be found here. VMware vSphere 6.0 documentation page including release notes, installation documents, upgrade documents, component documentation and so on can be found here.

This part of the blog series will cover the vSphere Fault Tolerance which is a feature that provides you zero downtime for a virtual machine (VM) during an ESXi host failure (hardware and/or software). The previous FT feature used VMware vLockstep technology which you can read more about here. The new FT version uses Fast Checkpointing that is very fast and permit continuous copying/checkpointing of the VM.

For a few years now the vSphere Fault Tolerance (FT) feature has been limited to protect VMs with one vCPU. I have seen technical previews of the feature supporting more than 1 vCPU a few times over the years while visiting VMworld events.

Now it is finally here and FT now supports 4 vCPUs. This includes the new setup of the FT protected VM which consists of one primary VM and one identical running copy of the same called secondary VM:

  • one configuration, .vmx, file per VM (primary and secondary). This is same as previous version
  • separate VMDK (disk and disk configuration files). This is NEW in this release of FT.
  • Allowed to be on different datastores. This is NEW in this release of FT.
  • Does not require Eager Zeroed Disk, can use any disk format. This is NEW in this release of FT.
  • Hot configure FT. This is NEW in this release of FT.

This means you can protect a complete other types of workloads and one that pops up in my mind immediately is the vCenter Server. The vCenter Server is a critical component for traditional vSphere environments from a management perspective and from both a management and functionality perspective when you add services such as VMware Horizon View, vCloud Director and vRealize Automation.

At present time, 2015-02-09, before vSphere 6.0 GA VMware says the protecting vCenter Server using FT will be supported in some cases. I’ll update the blog post when i get more information.

Anyway, it’s great being able to add this new level of availability for the management component with a vSphere out of the box (OOB) feature.

Because of the Fast Checkpointing technology the new FT feature is more resource intensive and requires a 10 Gbps connection since data will be copied between the ESXi hosts running the primary and secondary VM. A maximum of 4 VMs or 8 vCPUs can be protected per ESXi host, whichever limit is reached first.

The third blog post in the series covers Multi-Site Content Library and can be found here.

vSphere 6.0 configuration maximums can be found here.


Skip to comment form

  1. Mohsin

    The link that you shared for the documentation, still does not have content available for 6.0

  2. magander3

    yes i know that’s the case but the target link will be updated with the new content when it is released. I’ll remove the link if that takes 2 long.


  3. Nick Korte

    Was the requirement for FT 1GB before? I know this sounds a little crazy but do you see any Multi-Data Center FT coming out? With the 10GB requirement I am guessing not.

  4. Paulo Reis

    Improved fault tolerance vCPU allow us to use more applications with this feature.
    And use different datastore increase avalilability.

  5. ScoZel

    I tested this extensively during the beta and it works well! The only downside is the resource requirents limits the use cases.

  6. Yuri

    Really llike the improvements on the FT. Now I think that mosf of the companies will start using it for with most critical applications. Thanks for the insight

  7. Stayfans

    thx for the information.

  8. Mike Medrano

    Nice article. Good work!

    ~ Mike

  9. Looneyduk

    Nice work – direct and to the point.

    The upgrade of this feature to 4 vCPU, almost makes it worth trying out

  10. Zsolt Pamuki

    Tested on 5.5, I’m really curious about the new version.

  11. Jay Wright

    Cannot wait! FT that I can actually use. Thanks for the write up.

  12. magander3

    Let’s just hope vCenter Server will included in the VMs you can protect when the product reaches GA
    Then i will be totally awesome.

  13. Syed Fayyaz Hussain Rizvi

    Thanks for the write up man. FT is great with all new additions and enhancements.

  14. Cris Rodriguez

    Thanks! Another feature to test.

  15. Andres Rojas

    Great post!
    now FT really is up to the change with “real VMs”, good improvement

  16. Mohamed Ibrahem

    Thanks for the great post

  17. bob densley

    I’ll be very interested if FT can protect vCenter! I’ll keep my eyes on this post…

  18. Alessandro

    This part has been much improved.
    congratulations to vmware

  19. Amit Gumber


  20. Thomas True

    Hot configure – nice feature.

  21. vervoort jurgen

    nice. now i can protect other VM’s with FT too.

  22. Rahim

    Nice feature.. would have to upgrade ESX hosts 🙁

  23. Alex

    looking forward to being able to protect some machines now with this feature. 🙂

  24. Geoff Neish

    Does this mean I can now protect a vCenter server with FT?

  25. Andres Rojas

    Thx!, FT can now be used for real prod VMs which off course tend do to have more than 1 vCPU!

  26. Mohammed Sadiq

    Good Work .

  27. Stefan Schreiner

    Dear all,

    FT features sound promising, but right now I have to simple questions:
    – Installed ESXi 6 on two Dell R630 with two MD-Storages (FC) attached.
    – Created brand new guest virtual machine
    – Prepared NICs for FT and HA
    – Activated FT for this Guest OS (Win 2008 R2)

    Now I can not find the setting to move the secondary VM to a defined (different) storage.
    Trying to use “move” only allows to move the Host, but not the storage (claims “legacy” version of FT).

    Any idea on this?

    Thank you! 🙂

  28. Shawn

    I am very excited to give FT a try. I’ll have to check now and see if Vcenter is now supported, this was one of the biggest things I was hoping for in FT. Having the maximum on the CPU opens a new world for FT I believe.

  29. Francisco Amadi

    Finally, the REAL FT has come! Thanks for the update

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