mysql-mmm

Using A Single Master - Slave

Asked by Paul

I have a client who wants to use MMM, but they are only running 1 Master and 1 Slave, can you let me know if this is a supported configuration and how to set it up.

I have added into the mmm_common.conf

<host db1>
    ip 192.168.0.211
    mode master
    peer db1
</host>

<host db2>
    ip 192.168.0.212
    mode slave
</host>

If I don't put the db1 into the host db1 section the agents do not start up with the following problem : -

Starting MMM Agent Daemon: Config entry 'host->db1->peer' is required because of 'mode master', but missing at /usr/share/perl5/MMM/Common/Config.pm line 327

I have tried t ofind the answers but not been able to find anything, thanks for your help in advance.

Can I also have the Read and Write functions on the Same IP and not 1 for read and 1 for write?

Many thanks

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Arjen Lentz (arjen-lentz) said : 		#1

What's the point of MMM if you're only using a single master anyway?
If you want MMM to be able to do its job, you can start using the slave as second master.

Using the non-active master as a read-only slave can be done, but has operational issues:
 - if the active master fails, you'd still need all writes and reads on the same machine.
 - when doing updates, you'd need to send the reads to the active master. same story.
 - other similar scenarios.

do be properly resilient, you'd need 2 masters and at least 1 slave, but preferably at least 2.

Can you help with this problem?

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