When it comes to implementing Virtual Volumes (VVols) you better be on time

I was conversing with one of our VVol engineers today after he mentioned that we have seen customers experiencing problems with using VVols due to time sync issues in their vSphere environment. These problems could of easily been avoided with some simple RTFMing.

VMware’s New Virtual Volumes (VVols) architecture has a lot of moving parts and one big requirement for those parts to all work together is to have time synced between them. The below diagram depicts the vSphere components that are part of the VASA 2.0 specification which defines vendor VVol implementations.


The vSphere 6 storage documentation states the following before implementing VVols:

  • Synchronize all components in the storage array with vCenter Server and all ESXi hosts. Use Network
    Time Protocol (NTP) to do this synchronization.

That means you must synchronize time across the same NTP source with every ESXi host that will use VVols, your vCenter Server, your storage array and your VASA Provider if its external and not built into the array. You might think that this is no big deal if you don’t do this but that’s not the case, here’s some scenarios where it will cause problems:

  • During the initial setup of VVols if the time between your vCenter Server and storage array are out of sync when you try and register your VASA Provider it will fail with a cryptic error message which won’t indicate that the failure was caused by time not being in sync..
  • Once you register your VASA Provider and try and use VVols if your ESXi hosts are out of sync as well you may not be able to create a VM on VVol storage. What could occur in this scenario is that the VVol datastore reports zero space available so you are unable to select it as storage device when creating a new VM. Again not something that you would attribute to time being out of sync.

There may very well be more issues with using VVols that occur due to time not being in sync between all components. There are also time stamps that are used with VVols that could potentially cause problems if the time is off. These issues may all not be obviously related to time so to save yourself from potential problems and troubleshooting just make sure you have all your clocks in sync.

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  1. I can understand why time sync is important, what i don’t understand is the cryptic error message…
    If it is that important why not program decent error messages?

    Oh and thanks for the blog, good read

  2. I’m guessing the error is a side effect of the time being off and not something they had initially planned to error capture hence the cryptic error. They probably should have a better mechanism to deal with time sync issues and report on them better.

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