I would advise against the mySQL 'sym linking' as it's too easy to screw things up.
Best to set a Cronjob to run '/scripts/updatemysqlquota' about 20 minutes or so before other updates that have to do with accounts. As to the space usage in the 'var' dir., depending upon your hard drive partitioning it could be easier to 'sym link' other files instead.
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