chusmaxl
Contributor
Contributor

Network isolation between 2 FT esx host

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In a vSphere FT cluster, if one of esx is lan isolated from the other...what will be the cluster behavior??? Which server has priority, primary or secondary?

Thanks for answers.

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RenaudL
Hot Shot
Hot Shot

In a vSphere FT cluster, if one of esx is lan isolated from the other...what will be the cluster behavior??? Which server has priority, primary or secondary?

What happens is that both VMs try to take control as they both consider the other one dead. Then they both race to lock a special file on the shared volume they reside on, an operation which is guaranteed to be atomic. Only one VM wins this race, becomes the primary, and the losing VM commits suicide.

To summarize it, you can't predict which VM survives, however FT guarantees you will never end up in what we call a "split brain" situation where you have 2 primaries of the same VM running.

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lamw
Community Manager
Community Manager

I believe best practice is to have 3 physical systems for VMware FT, the primary will send data to secondary through the FT logging network and receive acks back. I believe if there is no data coming back then primary considers the secondary to be gone and will try to spin up a new secondary but with a 2 host FT setup, FT will probably not work and the primary will be unprotected.

Here are some additional links that may be of use:

=========================================================================

William Lam

VMware vExpert 2009

VMware ESX/ESXi scripts and resources at:

VMware Code Central - Scripts/Sample code for Developers and Administrators

If you find this information useful, please award points for "correct" or "helpful".

RenaudL
Hot Shot
Hot Shot

In a vSphere FT cluster, if one of esx is lan isolated from the other...what will be the cluster behavior??? Which server has priority, primary or secondary?

What happens is that both VMs try to take control as they both consider the other one dead. Then they both race to lock a special file on the shared volume they reside on, an operation which is guaranteed to be atomic. Only one VM wins this race, becomes the primary, and the losing VM commits suicide.

To summarize it, you can't predict which VM survives, however FT guarantees you will never end up in what we call a "split brain" situation where you have 2 primaries of the same VM running.

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chusmaxl
Contributor
Contributor

Many thanks RanaudL. That helps me a lot.

Best regards.

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Smeagol
Enthusiast
Enthusiast

Nice info.

I wish political elections worked in the same way.

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