there are different schools of thought on this subject. We do a power down during our backup cycles every Saturday evening at 1am. Others will do this monthly. Others less often. With more real time 24×7 requirements, the simple power down and up is becoming harder to do. I am of the opinion that it should be done periodically and 6 months is too long. I look forward to what others have to say on this subject.
My opinion is that it depends on whether you have a hardware maintenance agreement or not and how much time you can afford to be down.
I prefer an actual power cycle. The system should be down long enough for components to cool near to room temperature before powering back up. This provides a tolerance test that isn’t available any other way. It also provides simple exercise of moving components such as disk arms — they can all fully move to their at rest positions and move away from them.
For disk drives (and arms), the power cycle can influence the amount of stiction that may grow over time from aging lubricants. If stiction is becoming a problem, it can become a major problem at the wrong time. Unfortunately, sometimes you simply have to shut machines down. Maybe you have scheduled maintenance to upgrade some controllers. Or maybe there’s a regional power outage. For whatever reason, you have the system powered off and you have a definite time you intend to have it powered back up.
That’s not the moment to discover that a drive isn’t going to power back up.
So, when it’s reasonable, I have full power cycles — including cool-down — at regular intervals. If a power related failure is going to happen, I want to minimize the chance of it happening when some unrelated other major issue is happening.