VIrtual Center unavailable - effects on Virtual Machines?

[nics30]

We have a virtual center server 2.5 which is installed on a virtual machine on one of our ESX Servers. THis virtual center server is coming down for maintenance patching (just windows security updates)

I would like to know the effects this would have on the other virtual machines in the same cluster being managed by this virtual center server. I expect them to continue running and to be able to connect to them via the VI Client to the ESX Server.

I know the following implications are valid:(Obviously I will not be able to manage the VMs through VC during the outage)

1)There will be no failover (vmotion) during the outage

2)THere will be no HA or DRS during the outage

3)There will be no reporting during the outage

4)Any configuration changes during the outage will not be recorded in the VIrtual Center database.

Are there any other effects on the virtual machine which I should be aware of?

[casselc]

HA will continue to work, other than that I think you've got it.

[nics30]

Thanks CaselC - can you tell me how HA can still work as HA is enabled through virtual center and when virtual center is down I cant see how vmotion can work?

Is there an article that states it works still? Or maybe you could shed a bit more light on this?

THanks

[casselc]

HA requires vCenter for configuration, but the failure detection and failover responses are handled by an agent on the ESX(i) hosts and don't require vCenter involvement or VMotion functionality.

The Availability guide covers the mechanics of HA: http://www.vmware.com/pdf/vsphere4/r40/vsp_40_availability.pdf

And Duncan's "deepdive" post is a good supplement: http://www.yellow-bricks.com/vmware-high-availability-deepdiv/

[nics30]

Thanks for this - I think this is for a later version of ESX though- we use ESX 3.5 UPDATE 2.

[casselc]

The majority of the information will still apply, but see this document for more VI3-specific treatment: http://www.vmware.com/pdf/vmware_ha_wp.pdf

The quote of interest is this: "If the VirtualCenter Management Server host goes down, HA functionality changes as follows. HA clusters can still restart virtual machines on other hosts in case of failure; however, the information about what extra resources are available will be based on the state of the cluster before the VirtualCenter Management Server went down."

So, it continues to work but can't leverage DRS recommendations for optimal placement of VMs.

[krowczynski]

HA and DRS will still work.

You mus tonly be afraid if Cirtual Center will be longer than the grace period (14 days) down.

[nics30]

Can you show me a kb article or vmware doc that says this?

[krowczynski]

Perhaps this could help you and don't worry about your infrastrcute if you are only installing windows patches you will not have any problems!

You can even make a backup of your databse and a snap from you machine if you want!!

[bulletprooffool · Accepted solution]

nics,

1)There will be no failover (vmotion) during the outage

HA does not use vMootion, it starts a new instance of the VM (it is a recovery, not a migrate)

2)THere will be no HA or DRS during the outage

The VC is only required to configure HA - the aam service is installe don the hosts and the hosts can continue to monitor each other etc, even if the VC disappears.

In addition, you could even get the VC to recover itself on another Hosts, using HA.

3)There will be no reporting during the outage

All hosts continue to generate logs, but of course, no VC specific logs will be generated as the VC is not running.

4)Any configuration changes during the outage will not be recorded in the VIrtual Center database.

Config changes made on the hosts will be updated once the VC connects to the host

Are there any other effects on the virtual machine which I should be aware of?

You will only lose functions that REQUIRE VC - ie vMotion etc.

[nics30]

Thanks bulletproofool - this is helpful.