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Are there significant differences between versions 5.1 and 5.5?

The server in question is used to host a medium-sized vBulletin forum.

The main benefit of 5.1 is it's available through apt-get.

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up vote 14 down vote accepted

These days, you can use MySQL 5.5 now. I have 5.5.9 in production right now and it's running great.

I have successfully scaled MySQL 5.5 with simple circular replication amonst 3 DB Servers. Here is the layout of each DB server and what's running

  • MySQL 5.5.9
  • 2TB RAID10 SAS
  • 192GB RAM
  • One monolithic 162GB InnoDB Buffer Pool
  • Dual HexaCore (that's right, 12 CPUs)

/etc/my.cnf has the following


Each MySQL Server contains

  • 942 client (tenant) databases
  • 935GB total data
  • 95% of the buffer pool is full on all three servers

After 1 year, it still runs like a dream because of using MySQL 5.5 and getting InnoDB to engage all 12 CPUs.

So, I am quite happy with its performance thus far and so it the client.

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good god - what type of site are you running/ who is your host? – JM4 Aug 14 '12 at 15:20
@JM4 I am the DBA for the host. The client has a multitenant database cluster (Right now 777 tenants 789GB [They archived their old clients]). Buffer Pool stays full all day long. – RolandoMySQLDBA Aug 14 '12 at 15:31
wow - impressive – JM4 Aug 14 '12 at 16:15

5.5 is a development release and not suitable for production. Unless you have a specific reason to, you should not even consider running 5.5 for any production use.

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This is no longer true. – mjallday May 16 '11 at 3:33
5.5 was released in December 2010. It's safe for production use, though the other comments here apply. My recommendation (like Jon's below) is that you should use the Percona Server variant of MySQL 5.5, though.. – cce Nov 15 '11 at 22:26
As others mentioned, time has passed since my original answer and the version is now suitable for production. – Warner Jul 17 '13 at 13:45

Neither. Use percona 5.1 with xtra-db. It's as fast as 5.5, and does lots of things MySQL should be doing. It's free, based on, and is binary compatible as a drop in replacement for MySQL. I've yet to have anything but good experiences running percona instead of MySQL. Make sure you set the default engine to innodb. Show engines; will show you are using xtradb instead of innodb.

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You should actually use mysql 5.0, the query planner does a better job with vbulletin than 5.5. We found several areas where 5.5's query planner resulted in worse performance overall than 5.0 and thus switched back.

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