vCenter Server on a MSCS Cluster

[ohliger]

Hi, can anyone point my to the benefits of implementing a vCenter Server on a MSCS Cluster. Reading the documents, my impression is that everything (vMotion, DRS) keeps working when the vCenter server crashes/fails. "Only" the access to the actual configuration of the clusters will not be accessible.

From the HA document I can only found this:

Clusters and VirtualCenter Failure

You create and manage clusters using VirtualCenter. The VirtualCenter Management Server

places an agent on each host in the cluster so each host can communicate with other hosts to

maintain state information and know what to do in case of another host's failure. (The

VirtualCenter Management Server does not provide a single point of failure.) 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.

[sflanders]

What do you mean by implementing VC on a MSCS cluster? Do you mean running the VC database on the MSCS cluster? Running the VC database on a MSCS cluster does not make VC highly available. Two important reasons why you might consider using MSCS for the VC backend database include performance (i.e. being able to read/write information to/from the database quickly - say for getting performance information) and preventing database lose.

[jbogardus]

Reference - http://communities.vmware.com/thread/177770

vCenter is involved in initiating VMotion and determining when DRS load balancing is useful so without the server online this functionality won't be available.

However, the critical functionality HA will remain functional as each host maintains knowledge of the HA configuration independant of vCenter after HA has been configured.

Many environments don't worry about maintaining high availability of vCenter. Steps normally will be taken to make it fairly quick to recover, but not automate the recovery as would be provided by a MSCS cluster. With a good understanding of recovering databases and reinstalling vCenter both the db and vCenter can be rapidly brought back online to meet most needs. In most cases, short term lose of VMotion and DRS don't have a signficant impact.

[ohliger]

First thanks for your answers ! We had a big invest to implement a SAN to build up a high available architecture for our major applications. In my point of view its the wrong way to plan/implement then a management architecture which can fail. Of course you have to evaluate the risk of failure, the risks based in that failure and the costs for implementing HA for management.

Our basic approach is to look for HA for the vcenter server. My approach was to impement two MSCS cluster for the vCenter application and the SQL database which are located on different ESX server. That is "more" cost intensive and may be also more complex in the architecture. Other guys of my company prefer the solution to build the vcenter and SQL server solely on different ESX server and implement HA based on the vcenter/vmotion feature. That is basically managing the management, don´t know if there is any concern.

So back to my question, what is the advantage of having the vcenter funtionality high available. With a failed vCenter server, both the HA and DRS is working. Of course DRS is working based on the information before the crash, but for major application you can implement dedicated ressource pools which prevent for failure.

[ohliger]

Thanks for your answer, you are right. Please see my answer to