SFF-8643 to SFF-8087 cable is used to connect devices with different interface types, specifically Mini SAS HD (SFF-8643) to Mini SAS (SFF-8087) connections. Here's what each of these connectors means:

SFF-8643 (Mini SAS HD): SFF-8643 is a high-density connector used in Mini SAS HD (High Density) applications. It's commonly found in enterprise-grade storage systems, RAID controllers, and other high-performance data storage setups. The SFF-8643 connector typically supports multiple data lanes, allowing for higher data transfer rates and improved bandwidth utilization.

SFF-8087 (Mini SAS): SFF-8087 is a standard Mini SAS connector that's also commonly used in enterprise environments. It supports fewer data lanes compared to Mini SAS HD (typically 4 lanes), which means it offers slightly lower bandwidth capabilities.

The cable you're referring to, an SFF-8643 to SFF-8087 cable, is designed to bridge the connection between devices with these two different Mini SAS interfaces. It allows you to connect a device with an SFF-8643 port (such as a RAID controller or host bus adapter) to a device with an SFF-8087 port (such as a backplane or storage enclosure). This enables you to use the higher-density SFF-8643 connector on one end and the standard SFF-8087 connector on the other, translating the signals and connectors for communication between the devices.

In practical terms, this type of cable is often used to connect newer storage components with Mini SAS HD interfaces to older storage enclosures or backplanes that have Mini SAS (SFF-8087) ports. The cable's purpose is to ensure compatibility between devices with different Mini SAS connectors.

When using such cables, it's essential to ensure that the cable is of good quality and meets the specifications of the devices you're connecting. This will help ensure reliable data transmission and proper functioning of your storage setup.