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Re: 5.1 to 5.5 upgrade causes significant write slowdown (MyISAM + indexes)
Posted by: Scott Nemes
Date: January 25, 2013 09:51AM

Yeah that is a lot of changes, but overall they are changes for the better it seems.

Are the drives in your new setup the same speed as the old setup? I'd also verify that the raid controller in your new setup is on par with (or better than) the old one.

As for the slave lag, that's a whole other can of worms. Since standard MySQL replication is single threaded, it can be slow to catch up and/or get behind easily if the master is busy. Another big factor is how the slave hardware / config compares to the master, mainly with drive speeds and memory allocations for the MyISAM key cache and InnoDB buffer pool (i.e. if the master has an InnoDB buffer pool size of 10G and the slave has an InnoDB buffer pool size of 2G, the slave can struggle if the master is actually using it's entire buffer pool). If those factors limit replication even further, you can be in for a rough time. The one config setting that makes a difference is sync_binlog, which can slow replication down a lot when enabled on the slave. However it defaults to being off, and I do not see it in your my.cnf, so likely that is already off (but worth verifying).

--
Scott Nemes
MySQL DBA

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Edited 1 time(s). Last edit at 01/25/2013 09:52AM by Scott Nemes.

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Re: 5.1 to 5.5 upgrade causes significant write slowdown (MyISAM + indexes)
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