Briefly: that's a great way to get a backup which is not actually an accurate and consistent representation of your database, unless everything about both your

Briefly: that's a great way to get a backup which is not actually an accurate and consistent representation of your database, unless everything about both your setup and the exact state of MySQL's memory and your write usage over the interval of your backup operation breaks in your favor. For more detail, see the part about "Copying Table Files" in the backup chapter of the manual.