[ The PC Guide | Systems and Components Reference Guide | System Case | Drive Bays ]

External Drive Bays

This is a bit of a misnomer, since external means "outside" and these drive bays are certainly inside the case. However, they are called "external" because they allow access to the device from the outside. Any drive that uses removable media or has controls that must be operated manually must go in an external drive bay. This includes floppy disk, CD-ROM, DVD, tape and removable-storage drives.

Front view of the external drive bays on a sample tower PC.
One 5.25" external bay, and one 3.5" external bay are open.

Original image � Kamco Services
Image used with permission.

On PC-based servers, hard disk storage today is now almost exclusively done using RAID, arrays of disks that are designed to be fault-tolerant. One advantage of RAID, when implemented correctly, is that it lets you detect and replace suspect disk drives without having to power off the system and disrupt those using the server. Unfortunately, this feature does you no good if you have to disassemble the PC to get access to the disks, which in regular PCs are installed internally! To support the useful "hot swapping" capability, newer server cases are usually equipped with special external drive bays designed to use the SCA SCSI interface. The hard disks are placed in carriers that allow them to be inserted into and removed from the system on the fly.

Front of a server case with the door open, showing three
hard disks in carriers with handles partially inserted
into three of the case's external SCA drive bays.
(SuperMicro's SC820)

Original image � SuperMicro Computer, Inc.
Image used with permission.

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