Depends on your actual storage needs. Generally SSD and mechanical hard disk **** used together.
Because SSDs are faster, mechanical hard drives have more storage capacity and a stronger erase life.
Desktop: chassis capacity is enough to meet the needs of two hard drives, SSD as the main hard disk (responsible for the system), mechanical hard disk as a secondary hard disk (responsible for software).
Notebook: Notebook in recent years can be modified SSD, but usually can only remove the original mechanical hard disk and then add solid state, because there is no extra location to install two hard drives, unless the computer comes with an optical drive to replace the hard disk in order to meet the simultaneous equipment of two hard drives.
Expanded Information:
Solid State Drives (SSD), or Solid State Disks for short, are hard disks made from arrays of solid-state electronic memory chips, consisting of a control unit and a storage unit (FLASH chips, DRAM chips, etc.). (FLASH chip, DRAM chip) composition.
Solid State Drive is identical to ordinary hard disk in terms of interface specification and definition, function and usage, and is also identical to ordinary hard disk in terms of product shape and size. It is widely used in military, automotive, industrial control, video surveillance, network monitoring, network terminals, electric power, medical, aviation, navigation equipment and many other fields.
The operating temperature range of its chips is wide, commercial-grade products (0~70℃) industrial-grade products (-40~85℃). Although the cost is higher, it is gradually popularizing to the DIY market. Because SSD technology is different from traditional hard disk technology, it has generated a number of emerging memory vendors. Manufacturers can build SSDs by simply purchasing NAND memory and matching it with the appropriate control chip.
The new generation of SSDs commonly use the SATA-2 interface, SATA-3 interface, SAS interface, MSATA interface, PCI-E interface, NGFF interface, CFast interface, and SFF-8639 interface.