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samlouis55
Enthusiast
Enthusiast

VSAN running on 1 Host for Energy Saving

Hello,

We are currently running 4 hosts in our Datacenter and we have not vSAN in production. We are thinking to migrate to vSAN in our next project. Currently, everyday due to electricity issue we are facing, we migrate all our important/critical VMs in one host and power down the other 3 hosts after business hours. In this case, I am anticipating what will be the best solution when we will be using vSAN. I am seeing two options:

     1. Have the critcal VMs running on SAN so that it can be running on one host. (as it is like now).

     2. Have those critical VMs running on vSAN with FTT=0 so it can be running in one host. Will the vsan datastore available using 1 host? (I have not tested if it is feasible but theoretically it should work)

What do you think about this?

Regards.

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6 Replies
zdickinson
Expert
Expert

Good morning, I think you're going to run into all sorts of problems trying to do this with vSAN.  Do not do this.  Thank you, Zach.

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samlouis55
Enthusiast
Enthusiast

Does that mean it is more advisable to run the VMs that will stay powered on in a SAN while the others will be on vSAN?

Regards.

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depping
Leadership
Leadership

vSAN requires a minimum of 3 hosts to function correctly, I do not recommend running with less than that (or 2 hosts and a witness), but running with 1 host is not recommended.

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zdickinson
Expert
Expert

It's really not advisable to do this.  I would be afraid of some sort of data out of sync issue.  Let's say you did the following:

1.)VMs that need to stay running are on SAN, all others on vSAN.

2.)Shutdown all VMs that you can.

3.)vMotion VMs you cannot shutdown to one host.

4.)Put hosts into maintenance mode.

5.)Power down hosts.

6.)Power on hosts in reverse order.

Steps 5 and 6 make me very nervous.  You will sooooo much data to sync and nodes don't come back up properly, in the same order, etc...  I could easily see data corruption.  Thank you, Zach.

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samlouis55
Enthusiast
Enthusiast

Thanks for your input. Regarding your considerations, here is what I think for now.

1. Having vSAN running on 3 hosts and have 1 Host running outside of vSAN

2. VMs that will need to shutdown will run on vSAN and I will be able to shut down all the 3 Hosts.

3. Important VMs (VCenter, AD, DHCP, DNS, etc..) will run on the host that is not part of vSAN. This host will stay powered on only to run those VMs.

I think I should be safe like this.

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zdickinson
Expert
Expert

There is still some risk there.  If you have a host running outside of vSAN, that means it needs to be outside of the cluster, and that means HA will not able to restart those if that host fails.  Thank you, Zach.

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