Backplanes

RAID arrays, by their very nature, often contain a large number of disks. Those disks generate a lot of heat, take up a lot of room, and present a connection challenge to any RAID controller. The solution that most servers have opted for is to incorporate a backplane into the chassis.

A backplane is usually designed to abut a cage, with each drive inserted into the backplane using a carrier. Strictly speaking, the circuit board is the backplane, but it's the whole assembly that makes the system work. Figure 11.4 shows an example of a backplane, cage, and disk in a carrier from a Dell PowerEdge 2400.

Figure 11.4. You can use a backplane and drive carrier to create a dense array of easily connected drives.

Note

The term backplane is used for any circuit board into which other devices can be attached or plugged. Backplanes have been used to describe all manner of things, even a server's motherboard. It is typical to find backplanes described as either active or passive. An active backplane has processing power of its own. A passive backplane offers only a mechanical connection.

Backplanes are helpful in that they allow for strategic placement of fans for heat dissipation, provide a secure and reliable electrical connection, and offer a system by which drives can be removed and added easily without having to open a server.