Comparing different editions for automatic failover

[SamAnwar]

Hi all,

I need to select a virtualization product for a new project (VMware, Microsoft or Citrix). I did a lot of reading and I am leaning toward VMware but I am worried about cost. The requirement is to have two physical hosts (for redundancy) connected to an external storage with the ability of performing automatic failover, so that if one host fails the second one picks up. I also need to be able to backup the whole configuration including all the VMs to tape so that I can recover if the whole facility is down.

My question is whether the High Availability feature that is included in the Standard edition can do that, or whether I have to also get the DRS feature or VMotion which are only found in the Enterprise edition.

Regards,

[RParker]

My question is whether the High Availability feature that is included in the Standard edition can do that, or whether I have to also get the DRS feature or VMotion which are only found in the Enterprise edition.

DRS / Vmotion is for LIVe VM's. So yes if you need these features, get Enterprise. Backups can be accomplished by using these:

esXpress.com

vizioncore.com - vRanger

[WillGreen]

Standard edition includes high availability (HA), but you need to be clear what your requirements are. VMWare HA detects if a physical host fails and starts the virtual machine on another physical host in the cluster. It's not a live transfer, the VM is booted on the other host. Can your applications start automatically at boot? What about if the server failed while writing data, will it recover? You may also need to consider database replication if your apps are DB-based.

VMotion performs life transfers of VMs between hosts and is used by the Distributed Resource Scheduler (DRS) to balance VMs between physical hosts as their load changes; it's not a high availability feature. However, you can use it to move live VMs off a host to perform maintenance. VMotion isn't included in Standard edition. http://www.vmware.com/products/vi/buy.html shows what the different editions include.

[SamAnwar]

Thank you for your detailed answer, Will.

Based on your answer, I guess the standard edition may be okay as my main goal is to minimize downtime and not necessarily eliminate it completely. the VMs will be running multiple SQL Servers and Web Applications so both will start automaticaly if the VMs are rebooted. Of course I would prefer not to worry about what happen to the database if it fail while writing data, but I am affraid the cost of the enterprise edition may be prohibitive.

I am still a little confused though. So if VMotion is not a high availability feature, is there any advantage for enterprise over standard in regard to High Availability? If so, how? Can VMotion perform live transfer of a VM to a second host if the first host fail with no interruption to end users?

Thanks again

[Dave_Mishchenko]

Vmotion provides HA in the sense that you can move a VM without interruption should the first host require emergency maintenance, but it does require that the host be working for the VM to be vmotioned from it. ESX 4.0 will include VM Fault Tolerance which will mirror a VM on 2 hosts so that the VM will continue to operate should the primary host fail. The Enterprise edition also includes storage vmotion which allows you to move a running VM from one storage LUN to another.

[SamAnwar]

Thanks for the clarification, Dave.

So is there anything in any current edition of VMware that can accomplish zero down time if one host goes down?

[SuryaVMware · Accepted solution]

Zero downtime there is nothing as of now ...

HA will ensure your VMs are powered on another node in a cluster, with HA enabled, in the event of host failure or isolated situation. HA can also power on a VM in the event of VM faiure as an expermintal feature.

DRS will dynamically loadbalance the resources across the cluster and ensure the resource availibility to the best for every VM.

vMotion is live migration of a VM across a cluster or a farm of hosts with compitable CPUs. But the hosting ESX server has to working inorder facilitate a vMotion of a VM.

svmotion is live migration of a VM across datastores, for example from a local storage to SAN/iSCSI based storage, while the VM is still serving.

SRM is the site recovery manager, that will let you to fall back to a alternative site in the even of entire site is down.

Fault Tolerance is the upcoming feature that will let you run your VMs uninterrupted, Zero-downtime in the event of H/W failure or any other kind of host failure.

For now you should be good with the standard edition, which supports H, since zero downtime is not what you are looking right away.

Hope this helps.

-Surya

[SamAnwar]

Wow, thanks for the comprehensive explanation. This clarifies everything.