Enterprise Hard Drives

So what is an enterprise drive?, it is not sadly a hard drive authorised by Starfleet to boldly go where no hard drive has gone before. It is a drive designed, manufactured and configured for use by the type of ‘enterprises’ that employ multi-user computer systems, server installations, networked systems and tiered storage arrays. Most if not all of the major drive manufacturers offer some form of enterprise class device, with Seagate’s Cheetah and ES as well as Western Digitals’ Velociraptor and RE2 and RE3 ranges being prime examples. So what does the term actually relate to? What an enterprise drive is, fundamentally stems from the demands such usage places upon it.

Drives are commonly required to be in constant, round-the-clock operation. They must deliver the highest possible performance without sacrificing reliability, and they must be able to function in demanding environments. Because of the nature of their use, maximising capacity is not always the primary goal, and as a result the drives are often offered in Gb sizes that the average domestic computing enthusiast would consider very small in relation to their cost.

So how are the various performance parameters achieved? Increased ‘Input/Outputs per Second’ (IOPS) result from higher rotational speeds and larger cache sizes, with the former commonly dictating the use of 2.5” diameter platters, even for 3.5” form factor drives. The smaller platters allow the spindle bearings to maintain stable head alignment at spin speeds regularly in the region of 15,000 rpm, and have the added benefit of reducing power consumption.

24/7 operation requires a higher standard of design, manufacturing tolerance and component quality. Because such drives are commonly housed in racks or enclosures with many other drives, fans and other motor driven devices, the ability to withstand vibration is a major consideration as is cooling, ventilation and airflow management. Increasing energy costs have meant that manufacturers have had to place a higher emphasis on the often conflicting demands of cooling and power consumption.

The performance required also dictates the use of an interface that can support it. SCSI and Fibre Channel (FC) devices were often the first choice and may still be, though Serial Attached SCSI (SAS) and even high-end SATA are becoming increasingly evident. Drive firmware is likely to be more complex to handle demand management or ‘queuing’ as well as more robust error detection and correction (EDC) functions. All the aforementioned performance considerations mean that one of the easiest ways to identify an enterprise drive is, not surprisingly, by its higher cost.

The increasing use of RAID systems combined with the increasing performance of conventional drives has meant that they are starting to be viewed as a viable alternative to the use of enterprise drives, but for applications that demand the ultimate in performance and reliability, the enterprise drive is likely to remain the weapon of choice. The quest for even higher specs has led to enterprise drives being used in RAID arrays and even the use of ‘short-stroking’ techniques. These involve the use of software that restrict the drive to using only part of the physical platter capacity, perhaps using only 10% of the overall sectors at the outer platter edges where access speeds are greatest. This also limits the time taken for the heads to reposition onto other tracks and also reduces the physical demands on the head actuator assembly. This obviously causes an associated reduction in capacity and increase in outlay for hardware so is likely to be reserved for ‘cost is not a factor’ applications.

It was widely forecast that Solid State Device (SSD) drives, using flash memory technology and without any moving parts would become preeminent in the enterprise market. Here their performance characteristics gave them an advantage and their smaller capacities were not a barrier. However, though they are being chosen for many installations the traditional rotating platter hard drive is still very much in evidence in enterprise form, and no doubt the traditional hard drive manufacturers will be striving to keep it that way.