HA and vMotion - Simple question

I've implemented HA on ESX boxes and it works.
My next step would be enabling vMotion.
Will combination of HA and vMotion produce a 0-downtime? (e.g - If esx-1 host fails, then HA detects the failure and vMotion moves it transparently to another host?)

Thanks.
elo-miloAsked:
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jameskeagieCommented:
HA will just force a restart of the VM on esx-1 - its just like a hard power shut down.  Vmotion needs a failover cluster to function on for transparent motion to the other host.
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elo-miloAuthor Commented:
"HA will just force a restart of the VM on esx-1 "
---- wrong, it will restart it on esx-2.

Question remains the same - is it possible to achieve 0-downtime with combination of HA and vMotion? (No DRS or FT)

Thanks.
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jameskeagieCommented:
Short answer - no.

With vMotion w/o a DRS you will have downtime.  Your VM on esx-1 would have a hard-reset and possibly lose data in the same way a real machine would lose data from a hard reset (i.e. not likely but possible depending on what was processing) and then your downtime would be the amount of time it takes for the machine to reboot (kicked off by HA) and hopefully all your services are set for boot and you don't have to configure it on reboot - and your downtime will be a few minutes - but no - sorry no 0 downtime it would be at least a few minutes.
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elo-miloAuthor Commented:
OK, so let me get it straight:
1. Combination of HA + vMotion will give the follwing sequence if the esx-1 goes down:
- HA detects the failure
- HA shots down VN on esx1
- HA powers the VM on on esx-2
------ In this case I don;t understand what is the point of having vMotion combined with HA (and no drs)?

2. Would it be correct to say that vMotion without DRS is befitial only for manually moving VMs between hosts without downtime?
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jameskeagieCommented:
elo-milo

You have it absolutely correct - vMotion without DRS is only beneficial for moving VM's without downtime between hosts - and without DRS it must be initiated manually.  I wasn't clear in my initial response - HA will force a reboot of the VM FROM esx-1 - obviously detecting the failure it will move to your failover host - in this case esx-2.

The main advantages of vMotion come with DRS - otherwise you could schedule a maintenance outage and move the VM in very short order to a new host and not even need vMotion (granted if you need zero downtime vMotion is still helpful for moving with no downtime).  With DRS you can distribute VM's between hosts to distribute load balancing - having a dozen machines float between hosts is a powerful tool.

So currently HA would detect the failure - it may not even get a chance to shutdown the VM if the failure is serious - would move the vhd to the second host - and reboot.  Depending on this requires as I said before that your VM servers are set for services to boot correctly and configurations to load etc. which may require some scripting or careful monitoring of which services are necessary at boot.

Hope that helped a bit!  
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elo-miloAuthor Commented:
Got it, thatnks for the explanation.
Last question - is there anything in MVware world that will aloow an automatic failover based on what happens INSIDE the virtual machine - for example if SQL service on guest operating sistem fails, then failover is initiated.

Thanks.
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elo-miloAuthor Commented:
Just increased the points.
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ashwin_kumar525Commented:
VMware can not track the applications running inside the VM, instead you can go for application level clustering. For SQL, you can enable MSCS and have a clustered SQL instance. same applies to any other application if they have clustering feature.
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jameskeagieCommented:
elo,

Have not gotten that far in my own use of VMware - but from what I know ashwin answered your last question correctly - you'd need an application cluster.
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