A disk array connects two or more disks through a single controller. To the computer, the array looks like a single volume. The controller shuttles data between each disk, allowing for more optimal SCSI usage. While one disk is writing a block of data, the other disk is available for the next block. In this way, data transfers can be two or three times faster than with a single disk. Disk performance is directly related to how fast the disk spins (rotation rate) and how quickly the drive head can seek, access, and transfer data.