Edit: After half day, my wife’s Mac started having the same problem. I have then applied the solution that I found in the Apple
Defragmentation In Mac
A simple question is what is defragmentation? Well, the answer is simple. It is a process of scanning the system so that the performance aspect becomes faster and efficient. Many people are not even aware that most of the actions that are performed on operating systems occupy some space in the hard drive. This is not only associated with downloading of files from the internet, but these files also accumulate by simply browsing on the web. These files when accumulates, gathers a large portion of the hard disk which tends to slow down the system.
The process of fragmentation creates when files are constantly created and removed. If you create a file which larger than the available space, the system will automatically break it into several pieces which are then saved into the first available space within the hard drive. When the user wants to access the file, the system tends to gather all the parts of the file which might take time in case the hard drive is overloaded.
The file system which are used on Mac operating systems are set to operate on a separate level of fragmentation. Such an action is quite normal and does not impose a significant change in its performance which means frequent defragmentation of the Mac hard drive is not essential.
However, in reality, the nature of the tasks performed the nature of the saved files, the order in which all the files are segmented within the drive as well as the random-access disk functioning can all have an effect of the resulting performance. Under general terms, not much degradation of performance occurs under normal usage conditions of Mac operating systems.
But, as you create and remove large number of applications as well as files, the main drive might get subjected to fragmentation which might show signs of slowing down of the file system performance.
Under such circumstances, two methods are recommended by apple Inc. Firstly- you can use the apple Drive Setup for the purpose of initializing the drive after creating a backup for your saved files and applications. After the process is completed, you can always restore your files back into the system. The second option can be to use a third party defragmentation application which is easily available on the Web.
A word of caution here is that during the process of reinitialization, the files saved on the hard drive tends to erase so, ensure that you have created a backup of all the important files on the Mac operating system as you will definitely want to restore the files back into the system after the completion of the initialization process.
The process of defragmentation requires a large amount of time in terms of disk activity because the scattered data has to be rearranged. However, there are some drive defragmentation applications which does not have the ability to recover from the problem completely in case the data is stored in a critical position within the hard drive. Under such a situation, might run into the risk of losing data stored in that specific location or all the data stored in the main drive. Therefore, it is strongly recommended to keep regular backups of the data, especially before giving it a defrag scan.