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Drive Capacity and Performance, by Guy Weavers of Seagate
As the size and complexity of operating systems, user applications and data files increase, so does the importance of disc drive capabilities to overall PC system performance and end-user productivity. Two of the most critical considerations in selecting disc drives for a PC system are capacity and performance. Disc drive capacity refers to the size of storage memory available on a disc drive. Disc drive performance describes the speed and efficiency with which data can be written to and read from a drive.
Reacting to the trends for richer and more intensive data storage and use, PC system integrators and designers are increasingly looking to the hard drive as a key component of the overall system performance. And they are increasingly specifying higher-capacity, higher-performance drives to their users so they can more efficiently manage and utilize their data.
Capacity: The Race for Space
A recent study by the University of California at Berkeley estimated that the amount of original digital content creation each year is about 1.6 million terabytes. As a result, there is strong demand for low cost-per-gigabyte storage solutions: high capacity disc drives.
There is no "optimum" storage capacity for a disc drive. Determining storage requirements can be difficult, primarily because each user has unique needs for data storage and access. What is "enough" storage to a casual PC user will be completely different from what is enough for an audiophile storing her CD-based music collections.
In general, however, users find it best to utilize drives with the highest possible capacity. Since storage needs over time invariably increase, and keeping in mind the trends driving data use, it is likely that any user will find greater use for storage capacity over time. Larger-capacity drives also protect users' overall PC investment by allowing room for growth in storage, resulting is less spending for upgrades as they evolve their data use. Smaller drives are more limiting to users as they experience the phenomenon of needing to do more and store more data over time.
As the table below demonstrates, the uses of extra storage space can quickly escalate.
Storage Requirements for Various Applications
Average Storage/ Data Type/Use
10 Megabytes
- 1 minute SDTV quality video clip
700 Megabytes
- 1 data CD ROM
1 Gigabyte
- 12 hours of MP3 audio files
2 Gigabytes
- 62 rolls of low-resolution digital film
2.5 Gigabytes
- Installation of Windows XP, Microsoft Office, Quicken, Netscape Navigator
6 Gigabytes
- Audiophile digitized music library
12 Gigabytes
- 6 feature length video movies
100 Gigabytes
- 1800 digital images, 4 hours digital video, 40 hours MP3 music, 15 games, 25 applications
The desirability of higher-capacity drives is well known within the PC industry. Computer Source Magazine, for example, says, "Not that many years ago a 20-Gbyte hard drive was seen as the biggest drive you'd ever need. How times have changed - 60-Gbyte+ hard drives are a thing of everyday life."
Performance: The Need for Speed
Within the hard disc drive, spindle speed plays the most important role in drive performance. Spindle speed is a measure of how many revolutions per minute the drive's platters can make. The faster the spindle speed, the faster the speed at which bits of data pass under the read/write head of the drive, and the faster data can move to and from the computer.
Intel has found in tests that, on average, PC systems are waiting on disc drives about 30 percent of the time, and that this wait time "dilutes software and system performance." Faster spindle speeds deliver greater productivity by enabling users to more quickly load and use applications and data files. For mainstream PCs, 7,200 RPM is quickly becoming an industry standard. Again, the improvement in spindle speed delivers significant boosts in the performance of typical applications.
Serial ATA
Most desktop storage systems today use a parallel bus interface referred to as Ultra ATA/100. The parallel ATA interface has been in use on desktop systems as the mainstream internal storage inter-connect since the 1980s (over 15 years!). Today's PCs demand higher speeds, more robust data integrity and flexibility for innovative smaller designs. Physically and electrically, the current parallel bus has run into limitations that will prevent this bus from providing higher data transfer speeds. The move to a new technology is inevitable in the eyes of industry leaders such as Intel, Dell,
Seagate(r) and APT.
These same leaders formed the Serial ATA Working Group (serialata.org) and are dedicated to bringing this new technology to the forefront of today's PCs. Serial ATA is designed to overcome the limitations of parallel ATA while providing scalability for years to come. Setting the goal to be compatible and at cost parity with current parallel ATA drives when in volume, the Serial ATA Working Group is promoting the adoption of Serial ATA in all systems where ATA drives are being used today.
What is Serial ATA?
Serial ATA is a "serial" architecture as opposed to today's "parallel" ATA internal disc drive bus. Serial ATA wraps many bits of data into a packet and then at a higher speed (30 times faster) than parallel, transfers the packet of data down the wire to or from the host. In parallel drives today, Cyclic Redundancy Checking
(CRC) is performed on the data being transmitted back and forth-but is not performed on the commands. Serial ATA integrates CRC on both the command and data packet level for enhanced bus reliability.
Cyclic redundancy code detects all single and double-bit errors and ensures detection of 99.998% of all possible errors. A Serial ATA drive can transfer data at 150 Mbytes/sec on the bus to the host system with extremely reliable accuracy and the Serial ATA interface will continue to allow scalability for a very long time.
Additional Benefits
Serial ATA, an innovative new interface, allows continued performance growth, enhanced data reliability, and overall improved system dynamics above and beyond what parallel can efficiently continue to provide. Still in its early market-entry stage, Serial ATA provides immediate benefits to desktop users.
In addition to a faster, more reliable bus, Serial ATA improves cabling and connectors for a robust yet simpler integration. Gone are the days of bent pins, clumsy cabling and needlessly returned hard drives. Serial ATA cables are thinner and longer for improved system airflow and innovative system designs such as small form factor and consumer electronics boxes. Connectors are easier to snap into place in a "blind-mate" fashion, without any pins. Without the wide cables, system integrators can easily route the longer data cables (1 meter) within the system for simplicity or innovative designs.
Acoustics
Different markets have different requirements for sound power acoustics. Standard PCs (with fans) typically require drive acoustics in the sub-30-dB range for idle and can accommodate seek acoustics that are 3–4 dB higher than idle. Newer emerging markets, such as consumer electronics or internet appliances, may feature fanless products operating in very quiet environments; if so, acoustic requirements for these systems may need to be in the mid-20 dB range, with seeks less than 2 dB louder than idle.
Regardless of a drive's specifications, the most important factor to a user is how loud the drive sounds when it's built into a system. Many factors influence the overall noise or perceived noise of a system, including fans, prominent tones, structure-borne noise caused by vibrations transmitted or amplified through the system chassis, airborne noise muffled by the system case, differences between idle and seek noise, overall system design and drive mounting systems (isolators).
Seagate has performed extensive research and development of both quieter drives and better system designs to minimize the perceived acoustics of drives and systems. We call the resulting set of features
"sound barrier technology" (SBT). Seagate is leading the industry in not only providing exceptionally quiet drives but also understanding how drives sound when they are in systems, and designing methods, models and products to minimize overall system noise. These efforts are resulting in ever-quieter disc drives from Seagate and better system designs by OEMs and integrators, which ultimately results in more satisfied customers and
end-users.
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