[Building Sakai] innodb plugin

[Charles Hedrick]

Is anyone running with the Innodb plugin? I"m testing our a new database server. I duplicated a problem that I saw on our production server, although only when I was load testing. I simulated 200 students starting a test at the same time, using the direct link into the test. This turns out to be much worse than one would hope, because a critical table isn't indexed. 

WIth 100 users the test on the new system took 2 min, but only if I told innodb to use only 8 threads. This is a VM that has 18 virtual cores (hyper threaded system). No matter how many threads I used, CPU stayed at 33% or below, and there were periods of zero.

My reading is that there is contention, which is of course a known issue with Innodb on multicore processors. I've never seen that pattern of < 95% usage on our production server, which is an 8 core physical system (hyper threading off) running Solaris 10.

I decided to enable the innodb plugin. This is a two-line change to my.cnf. It uses a loadable library rather than the built-in innodb code. There should be no incompatibilities as long as you don't move to the new table format. The result was that my test used 95% of the CPU and took 19 sec.

This is clearly the way to go, if it doesn't cause trouble. Unless we see a performance disaster and have to move to the new configuration (which is possible), I'm going to keep the new database server in testing for a while, probably until Spring break.

The new server is part of our new fully virtualized infrastructure. It's on a new dual Westmere system (6 cores each), hyper threading on, Ubuntu server under Xenserver, with 3/4 of the cores assigned to this VM. File storage is a Dell MD3600i iSCSI system, connected with 10 G Ethernet.

We're already using Xenserver for our production front ends. The database systems are next.