[Question] High Availability for Compute (Hypervisor) nodes

asked 2015-05-04 06:30:23 -0600

tkmanh gravatar image

Hello All,

I have one question about High Availability for Compute (Hypervisor) nodes. If I have some ESXi compute nodes or KVM compute nodes and we need high availability for these nodes in case one of these nodes fails, what will provide high availability for these compute nodes? OpenStack provides or the hypervisor itself provides?

Thanks in advance.

Best regards,

Khiet Manh

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answered 2015-06-03 02:14:28 -0600

sgordon gravatar image

Running openstack-nova-compute in a horizontally scaled out fashion (e.g. two instances pointing to one ESXi cluster via the vCenter driver) is not currently recommended and there have been issues with this e.g.:

An alternative in the mean time could be to run the openstack-nova-compute service on the ESXi infrastructure itself in a single VM and use vCenter's HA support to keep it up. This does introduce a certain amount of a chicken and egg situation (though arguably no different to the KVM driver where the compute service also runs on the host it is managing) but avoids the potential issues currently inherent in running multiple instances of the service pointing at a single ESXi cluster (I say potential as there is limited testing in this area).

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answered 2015-06-02 22:36:33 -0600

dodi gravatar image

It depends on the hypervisor type. For VMWare you will need the vCenter to enable HA and will handle the High Availability similar to XenServer. However for the KVM Based Hypervisor, you will need to incorporate the use of the host-evacuate api from openstack.

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I believe the question is actually about making the openstack-nova-compute service itself HA. In a KVM deployment it's typically not a consideration as there is a 1:1 relationship between compute hosts and openstack-nova-compute services (if the service is down, it's typically because the host is).

sgordon gravatar imagesgordon ( 2015-06-03 02:09:56 -0600 )edit

@sgordon - I agree. someone has to be a bit creative with the monitoring script (a watchdog + haproxy + keeplalived) type of play for the ESXi nova-compute service. For the KVM as your statement with the 1:1 relationship, a script to trigger host-evacuate will do but needs common storage like Ceph.

dodi gravatar imagedodi ( 2015-06-03 08:41:33 -0600 )edit

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Asked: 2015-05-04 06:30:23 -0600

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Last updated: Jun 03 '15