It is to be noted that modern terabyte size disks and RAID arrays have longer data recovery times when they fail because of increased capacity which reduces performance.
How to maintain disks
Microsoft created disk cleaning as a maintenance program for their Windows operating system.
The tool searches your hard drive for files you no longer require, such as temporary files, cached webpages,and rejected things that wind up in your system's Recycle Bin.
Continuously updated data becomes physically fragmented over the disk area and requires regrouping.
An optimizing program is executed on a regular basis (daily, weekly, etc.).