The latest from the MySQL community

I'm looking at the schedule for Percona Live UK coming up in 2 weeks from now and realize there's quite a smorgasbord of High Availability talks. What's more interesting, I see that we will be presenting some opposite opinions for the audience to digest:

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Update 2012-01-09: I have now been able to understand the poor(ish) results in this benchmark. They are very likely due to a bad hardware setup and neither Galera nor InnoDB is to blame. See http://openlife.cc/blogs/2012/january/re-doing-galera-disk-bound-benchmark

People commenting on my results for benchmarking Galera on a disk bound workload seemed to be confused by the performance degrading when writing to more than one master, and not convinced at my speculations on the reasons. Since sysbench 0.5 has the benchmarks in the form of LUA scripts, it was temptingly easy to tweak those a little to see if my speculations were correct. So yesterday I did run tests again with a slightly modified sysbench workload. …

2 concepts I've been an active advocate of during the past few years are both supported by Galera: Multi-threaded (aka parallel) slave, and allowing out-of-order commits on such a parallel slave. In trying to optimize Galera settings for the disk bound workload I just reported on, I also came to test these alternatives.

Single threaded vs Multi threaded slave

All of my previously reported tests have been run with wsrep_slave_threads=32. For the memory-bound workload there was no difference using one thread or more, but I left it at 32 "just in case". For the disk bound workload there is a clear benefit in having a multi-threaded slave:

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Update 2012-01-09: I have now been able to understand the poor(ish) results in this benchmark. They are very likely due to a bad hardware setup and neither Galera nor InnoDB is to blame. See http://openlife.cc/blogs/2012/january/re-doing-galera-disk-bound-benchmark

After getting very good results with Galera with using a memory bound workload, I was eager to then also test a disk bound workload. Also this time I learned a lot about how Galera behaves and will try to share those findings here.

Setup

The setup for these tests is exactly the same as in last weeks benchmarks, except …

So, vacation is over and I was in luck: Already during first week I had ample time to finally put Galera replication to the test. It was a great experience: I learned a lot, and eventually got the great results I was hoping to see.

Again I've started by just running the standard Sysbench oltp read-write test. Since this is a commonly used benchmark, it produces numbers that are comparable with others running the same benchmarks. Including, as it happens, Galera developers themselves.

These tests were run on an 8 core server with 32 GB of RAM and the disk on some EMC device with a 2,5GB write cache.

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A while ago Baron blogged about his utter dislike for MMM, a framework supposedly used as a MySQL high-availability solution. While I have no personal experience with this framework, reading the comments to that blog I'm indeed convinced that Baron is right. For one thing, it includes the creator of MMM agreeing.

Baron's post still suggests - and having spoken with him I know that's what he has in mind - that a better solution could be built, it's just MMM that has a poor design. I'm going to go further than that: Personally, I've come to think that this family of so called clustering suites is just categorically the wrong approach to database high-availability. I will now explain why they fail, and what the right way is instead.

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I've been following the Galera project for years now, but this week I finally had some time to spend hands on time on it. I'm sure you noticed Vadim from Percona is also looking at it, it will be interesting to compare results. In this post I will just share the experience of installing and configuring Galera.

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Couple of Fridays ago we had one of our @Inuits days again. Rather than having some people give talks and presentations about what they have been doing for the past couple of months this time we set out to research, test, and build stuff.

We split up in 3 different groups, one focusing on CI and testing freshly build stuff with cucumber, a second one setup and tested Galera

We setup a 3 node Galera cluster , not really as smooth as we'd like to ..

Our first bump was that the installation of the package on CentOS is hell, it needs manual interaction such as replacing packages. Deploying this from a repository is probably not going to be a straight forward option.

Galera only takes care of replicating data, just as with MySQL MM replication there still is a need for an external …

This Thursday (February 11th, 14:00 UTC), Seppo Jaakola & Alex Yurchenko will talk about MySQL Galera Multi-Master Replication. Galera provides synchronous multi-master replication and uses a certification-based replication method for replicating transaction write sets in a DBMS cluster. The replication method requires close co-operation with database transaction processing and DMBS must support a specific replication API to be compatible with Galera. Codership has integrated Galera replication in the InnoDB storage engine, and the resulting MySQL/Galera cluster product has been published as a production-ready GA release in December 2009. The MySQL/Galera release 0.7 is available on the Codership and …

This Thursday (February 11th, 14:00 UTC), Seppo Jaakola & Alex Yurchenko will talk about MySQL Galera Multi-Master Replication. Galera provides synchronous multi-master replication and uses a certification-based replication method for replicating transaction write sets in a DBMS cluster. The replication method requires close co-operation with database transaction processing and DMBS must support a specific replication API to be compatible with Galera. Codership has integrated Galera replication in the InnoDB storage engine, and the resulting MySQL/Galera cluster product has been published as a production-ready GA release in December 2009. The MySQL/Galera release 0.7 is available on the Codership and …