A tape system usually comprises lots of tape drives, several thousand or even tens of thousands of cartridges, robots, software applications and machines which are running these applications. All involved components are able to log failures and statistical data. However, correlation is a laborious and ambiguous process and a wrong interpretation can easily result in a wrong decision. A single defective drive or cartridge can silently put the data on many other cartridges at stake, so it is extremely import to discover problems as early as possible. The longer it takes to identify and isolate a defective component the more extensive is the damage. To be able to take the right decision at the right time an effective monitoring system is essential. But how effective is the monitoring system? Is there any off-the-shelf software which can do the whole work for you? This paper is going to give an insight into the failures of the tape drives and tape cartridges we have been experiencing over the years at GridKa and the procedures we have developed to keep the data on tape as safe as possible.