Yellow Bricks

by Duncan Epping

Server

How to login to the vCLS VMs!?

· · 2 Comments

I was asked this question this week, how you can login to the vCLS VMs. Now before I share the video, I want to mention that I do not encourage people doing this, but as it is documented and supported I do want to provide a simple “how to” for how this works. If you want to login to the vCLS VM, maybe for troubleshooting if needed or for auditing, you can do so by SSH’ing first into your vCenter Server. When logged in to the vCenter Server you run the following command, which then returns the password, this will then allow you to login to the console of the vCLS VM. Again, I do not want to encourage you to do this. Either way, below you find the command for retrieving the password, and a short demo of me retrieving the password and logging in.

/usr/lib/vmware-wcp/decrypt_clustervm_pw.py

 

Which vSAN policy changes will trigger a rebuild?

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A couple of years ago I did a VMworld session with Cormac and we discussed the top things everyone should know about vSAN. One of the items discussed was which policy changes would trigger a rebuild. We tested the various situations and documented them. Two weeks ago a question around this was asked on a VMware internal Slack channel so I shared our findings. Considering it is already a few years ago, I wanted to make sure that our documented findings were still valid, so I redid the tests.

Now before I provide a table with the findings, I just want to explain what I tested, what I did is I created a VM with a default policy. I dumped a bunch of random data on the two VMDKs attached to the VM, and I then changed the policy of the VM while the VM is running. After changing the policy I verified through the command-line, and UI, if a rebuild of the objects was occurring or not. In some cases a policy change does not require a rebuild, while in other cases it does. This, of course, depends on what is being changed within the policy, and what that means for the objects associated with the policy. Hopefully, you will find the below table useful.

 

FromToResync
RAID-1RAID-1 with higher FTTYes
RAID-1RAID-1 with lower FTTNo
RAID-1RAID-5/6Yes
RAID-5/6RAID-1Yes
RAID-5RAID-6Yes
RAID-6RAID-5Yes
Stripe width 1Stripe width increase by 1 (or more)Yes
Stripe width xStripe width decrease by 1 (or more)Yes
Space Reservation 0Increase to larger than 0No
Space Reservation >= 1Increase by 1 (or more)No
Space reservation > 0Decrease to 0No
Read Cache 0Increase to larger than 0No
Read Cache >= 1Increase by 1 (or more)No
Read Cache >= 1Decrease by 1 (or more)No
Checksum enabledChecksum disabledNo
Checksum disabledChecksum enabledYes

Did you know vSphere 7.0 Update 1 also has a Skyline Health Check for vSphere Clustering Services?

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I did not know this, but yesterday the PM for vCLS reached out to me and informed me that we now have a Skyline Health Check as well for vSphere Clustering Services. The funny thing is that I actually requested this health check to be added after having a discussion on the topic of vCLS with the PM. Very impressive how fast the engineering team managed to include an additional health check for a brand new feature, this close to the release. I created a short demo, which shows you where you can find the vSphere Skyline Health option in the vSphere Client, and of course, it shows the vCLS Health Check being triggered. If you see the health check triggered, you can as mentioned enable retread mode and disable it again, this will provision a fresh set of vCLS VMs. How you do this you can find in this “considerations blog“, or simply watch the demo I shared here.

Demo Time: How to delete the vCLS VMs

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As I have a bunch of questions around how you can delete the vSphere Cluster Service VMs (vCLS VMs) I figured I would create a quick demo. It is pretty straight forward, and it should only be used when people are doing some kind of full cluster maintenance. This demo shows you how to get the VMs deleted by leveraging a vCenter Server Level Advanced setting (config.vcls.clusters.domain-c<identifier>.enabled). I have also written a post which has a bunch of requirements, Q&A, and considerations for the vCLS VMs, if you are interested in that read it here. Note, if you have a resource pool configuration, enabling “retreat mode” (disabling vCLS)) doesn’t impact resource pools in any shape or form, it just impact DRS load balancing. Anyway, I hope you find the demo useful.

How to delete a vCenter Server advanced setting

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I had a customer asking this week how he could delete an advanced setting that he had incorrectly added to vCenter Server. Some of you may have found yourself in this situation as well where you realized you made a typo while creating an advanced setting for the vCenter Server configuration. Unfortunately, there’s no option to delete an advanced setting in the H5 interface, but you can manually remove them via the command-line. It is rather straight forward:

  • SSH to you vCenter Server
  • Go to the “shell”
  • go to director: /etc/vmware-vpx/
  • Edit the file “vpxd.cfg”
  • Simply find the entry and delete the entry (with “vi” you use “/” to search)
  • Restart VPXD by running the following command 
    service-control --restart vmware-vpxd

And that is it, now your advanced setting should be cleared, I will put in a request though for a “delete option” in the H5 interface.