Hard Drive Info

Today’s harddisks are also mechanical parts that use spinning platters and read/write heads to store or read information from them. That also explains why harddisks haven’t seen the rapid pace of innovation as for example CPUs have; simply because the mechanics are holding the harddisk back from making similar leaps in performance. But to be honest that’s not entirely accurate, modern harddisks could be substantially faster, but not without either driving up the price significantly or introducing unwanted side effects.

One of these side effects is excessive noise; because a harddisk has a number of spinning and moving parts it is virtually impossible to make a harddisk noiseless. Anything you’ll do to counter the noise will either influence the performance, drive up the price, or make the harddisk physically larger. For example one way to reduce the noise would be to reduce the rpm of the platters which would mean we’d end up with a slower harddisk overall. And vice versa, by increasing the rpm of the platters we’ll get a better performing harddisk but the noise level will also increase.

Naturally we could counter the noise production by adding sound insulation. Unfortunately insulation is not the preferred way of tackling the noise production as it’ll make the harddisk physically larger, and thus leave less room for storage capacity. Furthermore it also works as an insulator for the heat produced by the harddisk, which would then cut into the harddisk’s MTBF, Mean Time Before Failure. That actually brings us to the second unwanted side effect of high-performance harddisks and that’s excessive heat production.

Modern IDE harddisks feature platters that revolve at either 5400 or 7200-rpm and thus revolve at about half the speed of the fastest SCSI harddisks that top out at 15,000-rpm. The main difference is that these SCSI harddisks are used in professional applications such as database servers where noise- and heat production are second to performance, and thus these levels are substantially higher than consumer level products. In consumer level PCs however heat production is becoming an increasingly important issue. PCs continue to get smaller and CPUs on average dissipate more than 50-watts of heat, so the system temperature will rise significantly if a harddisk is mounted with excessive heat production. In the following pages we’ll take a look at all recent 5400 and 7200-rpm harddisks from IBM, Maxtor, Western Digital, Seagate and Samsung with a focus on noise and heat production as well as overall performance.

As mentioned a modern harddisk still is a mechanical device, and as with most mechanical devices it is hard to completely cancel out all noise. One part that contributes to the noise significantly is the spindle, which drives the platters. The spindle is usually direct-driven and has an rpm of 5400 or 7200-rpm, which translates itself into a high-pitched whine. Harddisks that use high-quality bearings or even fluid-bearings are less noisy in this respect than others that use conventional bearings. Then there are the harddisk platters; due to the high speed at which they revolve they generate both noise and heat. And naturally the more platters, higher capacity harddisks, the more heat and noise are generated. Due to space constraints modern harddisks don’t use more than four platters which does limit the heat and noise production to a certain level.

Fortunately a manufacturer has a number of options at hand to reduce the noise level of the spindle and platters, such as using high-quality bearings or decoupling the spindle and spindle-motor from the harddisk casing by using a sound and vibration dampening gasket. Of course another way to reduce the noise and heat production would be to use less platters of a higher density, as this will not influence the storage capacity of the disk.
 

Fig 1. The interior of a typical harddisk whilst operating. This movie requires the Windows Media player to be installed and requires a broadband connection for streaming playback.

But there’s other moving parts that also contribute to a harddisk’s noise production; the read/write heads are notorious for causing the ‘rattling sound’ many harddisks make when accessing your data. And again the manufacturer has a number of options to reduce this noise which usually mean that the heads are operated less abruptly when sweeping across the platters. For example by smoothing out read/write operations by slowing the heads down when they need to reverse direction or by intelligently combining read and write operations and thus reducing head movement. Unfortunately many of these noise reducing measures do affect the harddisk’ performance and some can even be set arbitrarily through software to optimize for a specific application.

Any part that is operated above its maximum temperature rating over a prolonged period of time will see its MTBF drastically lowered. All parts that make up a modern PC have such a maximum temperature rating, most of which are around 50…65 degrees Celsius, or 122…149 degrees Fahrenheit. An average CPU dissipates about 50-watts of heat inside a PC case and is one of the major contributors to a rise in system temperature which could easily be as high as 45 C/ 113 F. If the case temperature is already that high, some of the parts of the PC could already be operating at or above their maximum temperature rating.

Especially 7200-rpm harddisks are suspect as they are known to get substantially hotter than their 5400-rpm counterparts. Naturally 7200-rpm and multiple platters all contribute to more heat being produced, as the spinning platters get hot due to the friction with the surrounding air and the heat dissipated by the spindle motor, the more platters and the higher the rpm, the more heat. Unfortunately we can’t simply say that 7200-rpm harddisks get hotter than 5400-rpm harddisks by default as our measurements will clearly show, but we’ll get to that in the next few pages.

Fig 2. The interior of a typical 80GB 7200-rpm harddisk, in this case a Maxtor D740X. This harddisk features two platters with 40GB/platter density and a total of four read/write heads.

What is important to consider though is the question whether the harddisk doesn’t get too hot when mounted inside the PC. Most modern harddisks have a maximum operating temperature ranging from 55 to 65 C or 131 to 149 F, and if operated above that temperature you’re really putting yourself at risk of losing valuable data or a harddisk malfunction. If the system temperature is already at 45 C/ 113 F the harddisk could very well be operating over it’s maximum temperature, which will cut into the disk’s MTBF and reliability significantly.

Hard Drive Info 2