You cannot have two instances of MySQL talking to the same set of files. Not even if everything is identical.
You can have two instances of MySQL, each with its own, separate, copy of the data.
You can have two instances of MySQL, one "replicating" from the other, with the same data, but separate disk files for this copies of the data.
When a single instance of MySQL is running with Barracuda, it can (in theory) have some tables that are using Antelope. The VARIABLE
in my.cnf
controls the "max". That is, when set to B, it can handle A or B. When set to A, it cannot handle B. (Note: they eventually eliminated both.)
Which do you really want?
innodb_large_prefix
is related. (Note, also, that it has been removed in a later release.) Perhaps this is really what you need -- 5 ways to deal with a certain error: http://mysql.rjweb.org/doc.php/limits#767_limit_in_innodb_indexes