Hard disks can also be chosen from Wide range of SSDs, SAS and SATA. Because this also greatly impacts server performance. You can change the drives at any moment you want. We can also add RAID Support in disks as well. So in case of drives failure your data will not be lost. You’ll always have a file backup in your hand.
Last but not the least, Processors which play an integral part in server performance. Because all of the processing is done using the processors. If every other component is fine but processor is dull then you are doomed. You need a processor which can easily scale with needs of enterprise level application.