Host failures with Virtual SAN - Set target recovery host

[lmigo]

Hi Community,

I've a question about host failures with Virtual SAN.

We've 6x ESXi hosts with (á 1 SSD and 7 HDDs) Virtual SAN enabled. So it is possible to lost 2 ESXi hosts without a failure. Correct?

Is it possible to set a host based rule who defines which is the target ESXi host in case of a failure?

For example:

When host 1/6 goes down, host 4/6 should start the VMs again.

When host 2/6 goes down, host 5/6 should start the VMs again.

When host 4/6 goes down, host 1/6 should start the VMs again.

When host 5/6 goes down, host 2/6 should start the VMs again.

Many thanks for your help.

Best regards from Germany!

[CHogan · Accepted solution]

Yes & no 🙂

To lose 2 ESXi hosts and continue to run all your VMs, you need to set the Number of Failures to tolerate = 2 in the VM Storage Policy and attach that policy to the VMs.

There is no way to create fault domains in VSAN currently however. So VSAN will determine where to rebuilt the objects when a host fails - this is not something you can control right now.

HTH

Cormac

[lmigo]

Hi Cormac,

thanks for answer.

One more: Is it possible to set "Number of Failures to tolerate = 3" in my scenario with 6 ESXi hosts?

[CHogan]

No, you will need 7 hosts to tolerate that many failures.

http://cormachogan.com/2014/05/15/vsan-part-25-how-many-hosts-needed-to-tolerate-failures/

[lmigo]

So is at the moment no possibility to work with Virtual SAN over two fire protected zones with full HA? (I know, VMware recommends virtual SAN limited per rack.)

For example 3 hosts in zone 1 and 3 hosts in zone 2.

[CHogan]

No - I'm afraid not. It is something we hope to introduce in the future (failure domains).

[lmigo]

Do you know when the feature "failure domain" will be implemented? 

More important, do you know whether it comes as a Virtual SAN update or as a standalone solution?

--

What do you think is best practice to provide VMs in HA mode in two separated fire protection zones with one vCenter instance?

Connection between the zones via Fibre and Copper is possible. Distance <60m.

[CHogan]

Unfortunately I cannot comment on any futures.

Regarding the separated zones, the issue you have is that you cannot tell VSAN to place one mirror on site A and another mirror on site B. This is the functionality that we are working on.

[lmigo]

Many thanks for your help Cormac.