The flash memory is typically NAND and may be connected via different interfaces such as SATA, SAS or PCIe. Server-side flash is often used as a high speed cache or in places where high IOPS (input/output operations per second) count.
Because server-side flash is dedicated to the server it’s installed in, it doesn't require as much capacity as array- or network-based flash devices. Implementation is also simpler than in a shared storage environment. Although flash capacity is significantly more expensive than hard disk drives, SSD caching or tiering can actually provide better performance at a lower cost.
Server-side flash advantages over disk array SAN storage include higher performance overall and higher performance per watt. It also dissipates less heat and makes less noise than conventional disk-based storage. However, lacking SAN-like features such as RAID and accessibility across networks make it unlikely to take over from storage arrays.