Basic question regarding VMHA

[JaiKishan]

Hi All,

I just want to clear that, does HA uses the concept of vMotion for the migration of the failed over host VM's to another host or does it have its own functionality to move the VM'sto the other host.

No where in the document I see anything mentioned about vMotion in HA?

"If vMotion is not configured on the cluster will the HA happen if a host has failed?"

Thanks,

J

[krowczynski]

HA means, if you host went down with some vms located on it, all the vms will be restarted on another host in the cluster!

MCP, VCP

[JaiKishan]

Hi,

My question is different, please read carefully.........

Thanks,

J

[mikeyhoward]

No HA does not use VMotion. HA simply restarts guest VMs from a failed host on alternate hosts within the cluster.

DRS uses VMotion to optimize resources.

Additionally when HA is restarting a guest VM, DRS will determine placement of that VM - i.e. which host the VM will be restarted on.

Prerequisites for HA are on page 20 of

I hope that helps you

[JaiKishan]

Hi Mike,

So if we have HA enabled, vMotion enabled and DRS enabled on our cluster, will HA use vMotion at that time, because before moving the VM's to another host DRS will do the space allocation and as you said DRS uses vMotion?

Please clear

Thanks,

J

[weinstein5]

No HA does not use vmotion ever - HA is designed to recover form a single host failureor to restart a VM if it is not functioning - so if a host is down vmotion will not work since it requires a fully functioning ESX server on either end of the migration with HA that is not the case.

And in the case if you are using HA to recover form a single VM failure vmtion still does not make sense because you will be migrating a VM that is crashed - so it will get restarted

DRS and HA are two seperate technologies - DRS will balance the VM workload in the case of an HA event once the VMs restart -

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[mikeyhoward]

In the event of a host failure, with HA enabled the VMs will be restarted on an alternate host. No VMotion required. DRS, if enabled, will place the restarted VM on an ESX host to optimize resources - no VMotion.

VMotion is the process of moving a guest VM live from 1 ESX host to another. VMotion can be initiated manually (right click migrate) or by DRS if DRS is set to fully automated and DRS believes that by VMotion'ing the VM to another host, the load is better balanced.

When a VM is being restarted, VMotion is not used.

Read in full the following docs...

- DRS from page 43