mysql-mmm

Why special machine is needed for monitor service?

Asked by Benik Bafuna

In the MMM documentation is required separate macheine for Monitoring service. Is it due to some technical or reliability reason?

Since we don't have any other available machine, is it somehow possible to make sure that Monitor shares machine(s) with mysql server?

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Arjen Lentz (arjen-lentz) said : 		#1

Well, if the MMM control process runs on the same physical box as what happens to at some point be the active master, and the box fails, then there obviously won't be any failover as MMM control will be dead at the same time. Running MMM control on the same physical box as one of the dual masters does not make a resilient environment. It defeats the purpose of having a failover system in place.

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ophion (danical) said : 		#2

Actualy with this schema the monitor is a single point of failure, and if this host fail all fail. Anyone knows if it is a problem include mysql-mmm-monitor in a cluster?

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Walter Heck (walterheck) said : 		#3

Nope, the monitor is not needed for MMM to work. If the monitor goes down, the virtual IP won't move anymore. That is not a situation that should last, but it doesn't disrupt service.

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ophion (danical) said : 		#4

thanks Walter

So it is no necesary having a cluster for the monitor, is it right?
The only problem is that if we lost the monitor host, we lost the control of replication so if we lost another host we could arrive to very bad situation but it is almost impossible.
thus a cluster isn't need. It's a realy good news.

thanks a lot

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