The specific application is a NAS that hosts media content and is frequently accessed during the day.
My NAS was probably cycling on and off around 5 times a day so I decided to not allow it to spin down. I'm thinking this will be better for the drive, but I am not sure.
I am wondering, however, if there is any concrete information out there as to what causes more detrimental wear on a hard disk: Spinning 24/7 or cycling on and off as needed?
The temperature cycling of them turning on and off is what really gets them. Drives last the longest when they transition from warm to cold the least. That being said, in most cases cycling a dozen times a day will take several years to build-up the wear necessary to cause a failure. My SAN runs the drives 24x7x365, but each case is different.
You should probably check technical details for your hard drive for maximum number of spin up/down events that it supports.
This information is available via smart so you can turn on spin-down, wait a few days and then check again technical specs if your drive will survive some lifetime you think is o.k.
Assuming decent server grade drives are used, experience indicates that you're best off leaving them spinning. Drives which are spun down or switched off tend to have a considerably higher failure rate.
The above doesn't necessarily apply to consumer grade drives due to their generally lower quality and wider manufacturing tolerances.
