You can sometimes repair these problems using Disk Utility, which offers two key tools, Repair Disk Permissions, and Repair Disk. When this happens your Mac can have a tough time finding or using that data, which slows down the overall performance of your machine. Sometimes information can be damaged in some way. This helps your operating system find the data and make sense of that information, retrieving it from storage on the disk or volume. Your Mac stores all your data in a directory on your disk. All your data is software, too, so even this can be affected. Macs are computers and like any computer the software on your disk can degrade. You are experiencing degraded system performance after a power cut.