A large amount of data in the data center is generated in various daily applications (such as some cloud applications, backup and archiving), which is not very high performance requirements for hard disk performance compared to data center business applications. The hard disk is required to have both large capacity and low cost. Therefore, we have seen that the hard disk manufacturers have not continued to develop higher-speed hard disks after the hard disk speed reaches 15k, but instead shifted the focus to improving the hard disk capacity. Recently, the 4TB large-capacity hard disk is already a mainstream market; and 5TB, 6TB or even Higher capacity hard drives are also gaining market share. On the other hand, in order to make the hard disk more suitable for cloud data centers and backup and archive applications, large-capacity hard drives will also be optimized for hard disk reliability and read/write control.