As I mentioned here, there is a slight change for enabling the [original] InnoDB Plugin in MariaDB 5.5 (as compared to how you would enable it in 5.1).

Remember, in MariaDB 5.5, if you do not “enable” (i.e., add anything to the config file to do so) the InnoDB Plugin in MariaDB 5.5, you’ll end up with XtraDB+ for your InnoDb plugin. However, if you do “enable” the InnoDB plugin, then you end up with the original InnoDB plugin provided by Oracle/InnoDB.

The change is that the plugin file (.dll for Windows, .so file for Linux) which was previously named “ha_innodb_plugin.dll” is now just “ha_innodb.dll”.

Thus, if you previously enabled the plugin with (would have been in a 5.1 instance):

[mysqld]
ignore_builtin_innodb
plugin-load=innodb=ha_innodb_plugin.dll;innodb_trx=ha_innodb_plugin.dll;
innodb_locks=ha_innodb_plugin.dll;innodb_lock_waits=ha_innodb_plugin.dll;
innodb_cmp=ha_innodb_plugin.dll;innodb_cmp_reset=ha_innodb_plugin.dll;
innodb_cmpmem=ha_innodb_plugin.dll;innodb_cmpmem_reset=ha_innodb_plugin.dll

You now need to use:

[mysqld]
ignore_builtin_innodb
plugin-load=innodb=ha_innodb.dll;innodb_trx=ha_innodb.dll;
innodb_locks=ha_innodb.dll;innodb_lock_waits=ha_innodb.dll;
innodb_cmp=ha_innodb.dll;innodb_cmp_reset=ha_innodb.dll;
innodb_cmpmem=ha_innodb.dll;innodb_cmpmem_reset=ha_innodb.dll

That is the only difference, so after making that change, just restart your instance, and you’ll be in business.

For reference, if you encounter this, you might see an error similar to the following in your error log:

120524 19:24:56 [ERROR] Can't open shared library
 'C:\Program Files\MySQL\MariaDB 5.5\lib\plugin\ha_innodb.dll'
 (errno: 0 The specified module could not be found.)
120524 19:24:56 [ERROR] Couldn't load plugin named 'innodb' with
 soname 'ha_innodb.dll'.
120524 19:24:56 [ERROR] C:/Program Files/MySQL/MariaDB 5.5/bin/mysqld:
 unknown variable 'innodb_buffer_pool_size=10M'
120524 19:24:56 [ERROR] Aborting

Hope this helps.