Yellow Bricks

by Duncan Epping

7.0u2

vSAN File Services fails to create file share with error Failed to create the VDFS File System.

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Last week on our internal slack channel one of the field folks had a question. He was hitting a situation where vSAN File Services failed when creating a file share with the error “Failed to create the VDFS File System”. We went back and forth a bit and after a while I jumped on Zoom to look at the issue, and troubleshoot the environment. After testing various combinations of policies I noticed that a particular policy worked, whole another policy did not. At first it looked like that stretched cluster policies would not work but after creating a new policy with a different name it did work. One thing left, the name of the policy. It appears that the use of special characters in the VM Storage Policy name results in the error “Failed to create the VDFS File System”. In this particular case the VM Storage Policy that was used was “stretched – mirrored FTT=1 RAID-1”. The character that was causing the issue was the “=” character.

How do you resolve it? Simply change the name of the policy. For instance, the following would work: “stretched – mirrored FTT1 RAID-1”.

vSAN File Services and Stretched Clusters!

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As most of you probably know, vSAN File Services is not supported on a stretched cluster with vSAN 7.0 or 7.0U1. However, starting with vSAN 7.0 U2 we now fully support the use of vSAN File Services on a stretched cluster configuration! Why is that?

In 7.0 U2, you now have the ability to specify during configuration of vSAN File Services to which site certain IP addresses belong. In other words, you can specify the “site affinity” of your File Service services. This is shown in the screenshot below. Now I do want to note, this is a soft affinity rule. Meaning that if hosts, or VMs, fail on which these file services containers are running it could be that the container is restarted in the opposite location. Again, a soft rule, not a hard rule!

Of course, that is not the end of the story. You also need to be able to specify for each share with which location they have affinity. Again, you can do this during configuration (or edit it afterward if desired), and this basically then sets the affinity for the file share to a location. Or said differently, it will ensure that when you connect to file share, one of the file servers in the specified site will be used. Again, this is a soft rule, meaning that if none of the file servers are available on that site, you will still be able to use vSAN File Services,  just not with the optimized data path you defined.

Hopefully, that gives a quick overview of how you can use vSAN File Services in combination with a vSAN Stretched Cluster.  I created a video to demonstrate these new capabilities, you can watch it below.

vSAN 7.0 U2 Durability Components?

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Last week I published a new demo on my youtube channel (at the bottom of this post) and it discussed an enhanced feature called Durability Components. Some may know these as “delta components” as well. These durability components were introduced in vSAN 7.0 Update 1 and provided a mechanism to maintain the required availability for VMs while doing maintenance. That meaning that when you would place a host into maintenance mode new “durability components” would be created for the components which were stored on that host. This would then allow all the new VM I/O to be committed to the existing component, as well as the durability component.

Now, starting with vSAN 7.0 Update 2, vSAN also uses these durability components in situations where a host failure has occurred. So if a host has failed, durability components will be created to ensure we still maintain the specified availability level specified within the policy as shown in the diagram above. The great thing is that if a second host fails in an FTT=1 scenario and you are able to recover the first failed host, we can still merge the data with the first failed host with the durability component! So not only are these durability components great for improving the resync times, but they also provide a higher level of availability to vSAN! To summarize:

  1. Host fails
  2. Durability components are created for all impacted objects
  3. New writes are committed to existing components and the new durability components
  4. Host recovers
  5. Durability components are merged with the previously failed components
  6. Durability components are deleted when resync has completed

I hope that help providing a better understanding of how these durability components help improving availability/resiliency in your environment with vSAN 7.0 Update 2.

I can understand that some of you may not want to test durability components in their own environment, this is why I recorded a quick demo and published it on my youtube channel. Check out the video below, as it also shows you how durability components are represented in the UI.