In fact, it's usually worse than that, because if you are using hardware RAID, you must also include the MTBF of the controller , which without the RAID functionality, wouldn't be needed. For sake of illustration, let's say the MTBF of the controller card is 300,000 hours. Well, that's the other side of the reliability coin. While the reliability of the array hardware goes down, when you include redundancy information through mirroring or parity , you provide fault tolerance , the ability to withstand and recover from a failure. This allows the decreased reliability of the array to allow failures to occur without the array or its data being disrupted, and that's how RAID provides data protection.
Fault tolerance is discussed here .
A striped array without redundancy has substantially lower reliability than a single drive and no fault tolerance. That's why I do not recommend its use unless its performance is absolutely required, and it is supplemented with very thorough backup procedures. This page has been served 5587 times. Copyright 1997-2001 Charles M. Kozierok . All Rights Reserved.