Just Don't (1 of ?)
Just don’t copy MySQL data files while the tables are in use and expect the backup to work.
The conversation was going to be a painful one, sysadmin, the hero of our story felt it in the stream of vindaloo sauce that passed as his blood. “I noticed that our MySQL backups are just raw copies of the data files. I also saw some errors from the tar command about the files being written to while the backup was being run.” “Yes, we know about that risk but if we ever need one of the backups we can probably repair the tables.” “But isn’t the worst possible time to try and repair tables when we have a broken system and need the actual data?” “We’ve never needed them so far. Anyway this doesn’t lock the database or slow it down.” sound of head hitting desk
If this is you PLEASE think about the possible options, a separate replication host that can be stopped and backed up, online backups (if you use InnoDB tables) or even (this is also bad) just a read lock and table by table SQL dumps are better than copying data you know is probably in an inconsistent state.