Problem Summary. If you are using Apple OS X Leopard Time Machine with an external drive, you may notice that your computer is slowing down for certain tasks which wake the drive from a sleeping state. Anytime you go to save a file, or need to access the finder, the computer will wake the sleeping drive and then pause for a few seconds while the drive spins up.
Problem Solutions. In power management settings the “Put hard drives to sleep when not in use” setting can be turned off to prevent this problem. However, you may want to eject (unmount) the backup drive when it isn’t in use. Since much of computing is redundant or performed in “the cloud” of the Internet, much data isn’t on local machines to be backed up anyway. Consider plugging in the drive twice a day, or after a major project, to get a quick backup automatically.