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Real World Experience
Posted by: Warren Konkel
Date: December 01, 2004 10:21AM

I am looking to speak with somebody over the telephone regarding their failure/success at setting up and maintaining a MySQL cluster. We're looking to upgrade a 1 master 1 slave MySQL setup to a 4 machine cluster in an attempt to handle scaling as well as fault tolerance. I have a 2 machine cluster setup and working and so far I am impressed, but there's still a lot of questions that need answering before we can move to MySQL clusters. Here are a few questions to get started:

1. I have two NDB nodes setup with NoRepliacs=2. This means that both contain a full copy of the DB (correct?). When I do a "SHOW" within ndb_mgm, why does one show up as a master? What is the significance of being a "master"? Do clusters use the master-slaves replication that exists in non-clustered MySQL? Does this mean writes can only happen on the master and not the slaves? If that's the case, then I assume that this is all handled automatically?

2. If this is an in-memory database, when I shutdown the cluster, does all data get wiped?

3. If the ndb_mgmd goes down and comes back up, when/how do the MYSQLD/NDB nodes rejoin?

4. Is it possible to "grow" or "shrink" the cluster over time? How does this work? Adding extra API nodes seems like it shouldn't cause problems, but what If I add more ndbd nodes allowing for further fragmentation? Does the cluster automatically redistribute all the data so the hash algorithm continues to work? Do I have to bring down the full cluster to do this? Is this even possible?

5. How will the cluster respond to upgrading to newer versions of MySQL as they are released? Can I upgrade node by node, allowing the cluster to stay active or do I need to bring the whole cluster down and upgrade it all at once?

6. Is MySQL cluster really stable and ready for production?

To summarize my concerns, I have a working cluster for testing and I am very impressed with how it works so far. However I am concerned about long term maintenance. If you have a few minutes and wouldn't mind describing your experiences with MySQL cluster I would be very appreciative. Feel free to e-mail or call me.

Warren Konkel
wkonkel @ mindshare . net

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Real World Experience
December 01, 2004 10:21AM
December 01, 2004 09:02PM

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