The hard disk is the main data storage device for your computer. Hard disks are generally located in fixed bays within the computer chassis. Some disks are hot-pluggable, meaning they can be removed and replaced while the machine is running, and the operating system will recognize the new disk without rebooting. Current generation hard disks range in size from 8GB to 146GB, although smaller and larger drives can be found. The most commonly used interfaces for hard drives are ATA (IDE or EIDE) and SCSI.
When selecting internal disk drive storage for your PowerEdge server, you have two options - ATA (or IDE) or SCSI. ATA is the de facto disk drive technology widely used for desktops and notebooks. ATA is also suitable for utility server functions, such as gateway, domain, and low-end file/print or caching servers. However, ATA is not optimized for running primary server applications on busy networks, especially as businesses expand and usage increases.
For E-mail, database, and web servers, all with high usage, performance is needed to keep your business productive and profitable. SCSI disk drive technology is quite often a more suitable choice than ATA in these cases for a variety of reasons: SCSI disk drives handle more requests per bus, deliver higher performance (faster maximum throughput) and spin faster to find and deliver information more quickly.