In an industry known for its cyclical up/downturns, the hard disk drive (HDD) market appears to be relatively stable. The TrendFocus market research firm expects HDD shipments to surge from 495 million in 2007 to 768 million in 2011, a compound annual growth rate of 11.61%. However, in a testament to the ongoing decrease in cost-per-gigabyte, HDD revenues are expected to grow from $31.3 billion in 2007 to $33.3 billion in 2011, a CAGR of only 1.56% (see figure, below).

For 2008, another market research firm-International Data Corp. (IDC)-predicts a near-double-digit growth rate of 9.3% in terms of unit shipments, fueled largely by the mobile segment of the overall drive market.

And in good news for the disk drive manufacturers that got battered in a volatile 2007, Needham & Co. financial analysts predict that 2008 could be the most profitable year ever for the HDD industry.

Form factors, rpm
Most disk drives come in either a 3.5-inch or 2.5-inch form factor. Whereas the 3.5-inch form factor has been the workhorse of the enterprise segment of the market (i.e., non-desktop/portable), the industry is migrating to the 2.5-inch form factor, which was previously relegated primarily to the laptop market segment.
“In the server space, the 2.5-in form factor is in use industry-wide,” says Marty Czekalski, senior manager of market development at Seagate Technology,

When you consider “speeds and feeds” in HDD technology, the pacing features are transfer rate and rotational speeds. In the enterprise segment of the market, rotational speeds are typically 10,000rpm or 15,000rpm for both 3.5-inch and 2.5-inch drives. How- ever, Hossein Moghadan, Western Digital’s CTO, notes that those rotational rates apply mainly to online, or primary, storage applications and that 7,200rpm drives are common in nearline, or secondary, applications.

Transfer rates generally scale with the rotational speed. However, Richard New, director of research at Hitachi Global Storage Technologies (GST), points out that there are two aspects to consider when you are examining transfer rates: the peak transfer rate, which is proportional to rotational speed and linear density, and the random access rate, which is driven by seek time and rotational latency.

Ultra-high-speed HDDs rotating at speeds exceeding 20,000rpm have been demonstrated in manufacturers’ labs, but they have not been commercialized due to heat generation, power consumption, noise, vibration, and other problems that generally suggest a lack of long-term reliability.


The venerable parallel SCSI interface is nearing its end of life. In an InfoStor reader poll, only 4% of the respondents said that parallel SCSI will be their primary drive interface over the next 12 months (see figure below).
But the heir apparent to parallel SCSI is still unclear. In that same InfoStor reader survey, 35% of the respondents cited Fibre Channel as their primary drive interface over the next 12 months, while 32% cited SATA and 29% said that SAS would be their primary interface.

IDC predicts that this year SATA will account for almost 40% of all enterprise-level disk drive shipments, followed by Fibre Channel at about 24% and SAS at 23% (see figure on p. 26). Somewhat surprisingly, IDC expects parallel SCSI to account for 12.7% of enterprise HDD shipments this year.

Gartner Dataquest’s predictions are somewhat different. In 2008, Gartner expects SAS to account for about 41% of multi-user HDD shipments, followed by SATA at 29% and Fibre Channel at approximately 23% (see figure below). Parallel SCSI is expected to have only a 7.3% market share.

Perpendicular recording
Improvements in read/write head technology and media technology are expected to match an expected 40% improvement in areal density over the next year. Many of the changes in heads and media technology took place over the last year or so as perpendicular magnetic recording (PMR) displaced traditional longitudinal recording. Perpendicular recording, which was introduced on 3.5-inch drives in mid-2006, is believed to be capable of delivering up to 10x the storage density of longitudinal recording on the same media.

“Perpendicular recording is here to stay,” says Dr. William Cain, vice president of technology at Western Digital. “The whole industry has switched to perpendicular recording over the last year.”

Perpendicular recording overcomes the constraints imposed by the “superparamagnetic effect,” which occurs when the microscopic magnetic grains on the disk become so tiny that ambient temperature can reverse their magnetic orientations, causing data loss.

In longitudinal recording, the magnetic orientation of the data bits is horizontal, or parallel, to the surface of the disk. In perpendicular recording, the magnetic orientation of the data bits is aligned vertically, or perpendicular, to the disk. With perpendicular recording, it’s harder to reverse the magnetic orientation of the bits.

Perpendicular recording has spurred further research into head and media technology. For example, Hitachi GST claims to have developed the world’s smallest read head for HDDs, which is expected to quadruple current drive capacity to 4TB on desktop drives and 1TB on notebook drives. But the heads-dubbed current perpendicular-to-the-plane giant magneto-resistive (CPP-GMR) heads-aren’t expected until at least 2009.

Powering down
Disk drive manufacturers are doing their part in the overall effort toward more “green” data centers. For example, some manufacturers have introduced “power-down” drives (also sometimes referred to as “sleepy drives”), where the drive spins down when not in use. This can be advantageous in disk-based backup arrays, virtual tape libraries (VTLs), and other applications where files are accessed infrequently. When files on powered-down drives are needed, the array starts them spinning again.
Powered-down drives don’t need cooling, which reduces an array’s overall power consumption.

Western Digital’s Moghadan cautions that a complete power down could draw too much wattage upon spin up. With that in mind, WD offers IntelliPower technology, which balances spin speed, transfer rate, and caching algorithms to avoid always spinning at top speed. Also, less current is used during spin up, allowing more drives to spin up simultaneously, which results in faster system readiness.

Similarly, disk-array vendors such as Copan (which pioneered the concept) and Nexsan have massive array of idle drives (MAID) technology, in which a proportion of drives in an array are shut down to save power. In Copan’s implementation, up to three-quarters of an array’s drives are powered down at any given time. This results in much less heat generation; also, more drives can be packed into an array. Fujitsu also offers MAID technology in its Eternus line of disk arrays.

On-board encryption
In an effort to address data security issues, HDD drive manufacturers are working on drive-level encryption.

Gianna DaGiau, senior marketing manager for Seagate’s Enterprise Compute Business unit, explains how the company’s Full Disk Encryption (FDE) technology works: “When you do a write, the cleartext enters the drive and, before it is written to the disk, it’s encrypted using an encryption key embedded in the drive. When the data is read, the encrypted data is deciphered before it leaves the drive.” Drive-level encryption is enabled by an ASIC on the drive that handles encryption

Seagate and other drive manufacturers already offer encryption on their desktop and notebook drives, but all vendors plan to add the option to their enterprise drives. Seagate, for example, plans to offer encryption on some of its enterprise drives later this year. The company claims that drive-level encryption will not negatively affect performance. As part of a deal announced at last fall’s Storage Networking World (SNW) conference, IBM announced that it will provide key management for Seagate’s encryption. LSI will also participate in the technology by developing controllers that work with the “self-encrypting” drives.

Mark Ferelli is a freelance writer. He can be contacted at [email protected].

Recent disk drive introductions
One of the major themes among disk drive manufacturers over the last year has been reduced energy consumption. Nowhere is that more evident than at Western Digital (WD), which has introduced GreenPower versions of its WD AV drives, dubbed AV-GP. Available in capacities of 500GB, 750GB, and 1TB, the SATA drives reduce power consumption by up to 40% compared to standard drives, according to WD. Technologies that contribute to lower power, cooling, and noise include the following:

  • IntelliPower: Balances spin speed, transfer rate, and caching algorithms to reduce power requirements and boost performance;
  • IntelliSeek: Calculates optimum seek speeds to lower power consumption, noise, and vibration; and
  • IntelliPark: Lowers power consumption by automatically unloading recording heads during idle mode to reduce aerodynamic drag and disabling read/write channel electronics.

Another recent entry in WD’s Green- Power lineup is the 3.5-inch Caviar GP 500GB SATA drive, which consumes only 3.3 watts in idle mode and 6 watts during seek mode. Estimated price is $150.
Fujitsu Computer Products of America is also stressing power reduction in its line of MHZ2 BH disk drives, which went into production shipments this month. For example, Fujitsu claims read/write power consumption of 1.9W and idle-mode power consumption of 0.6W.

Based on perpendicular magnetic recording, or PMR (see main article), the 2.5-inch MHZ2 BH SATA drives range in capacity from 40GB to 320GB and have a rotation rate of 5,400rpm. Other specs include a maximum buffer-to-host transfer rate of 150MBps, a read/write seek time of 12 to 14msec, and a track-to-track seek time of 1.5msec.

Samsung recently entered the “enterprise” (as opposed to desktop/mobile) hard-drive market with the F1 series of 1TB SATA drives. The 3.5-inch HDDs run at 7,200rpm and are based on a three-platter design with 334GB per disk. Samsung claims a power consumption rating of 6.7W in idle mode and 7.2W in random seek mode. The PMR-based drives include a 32MB cache and have a mean time between failure (MTBF) rating of 1.2 million hours. MSRP is $399.
Another recent drive introduction from Samsung is the Spinpoint M6 HM320JI, a 2.5-inch, 320MB, 5,400rpm SATA drive with 8MB of cache. MSRP is $249.

This month, Hitachi Global Storage Technologies (GST) began shipping the 2.5-inch, 500GB Travelstar 5K500 drives. Introduced at last month’s Consumer Electronics Show (CES), the SATA drives come in 400GB or 500GB capacities and include features such as Bulk Data Encryption (BDE) for security, 1.9W read/write power consumption and 0.7W idle-mode power consumption, a 5,400rpm rotation rate, 5.5msec average latency, and 12msec average read time. The drives have three disks and six recording heads and are designed primarily for notebooks and other mobile devices.

Seagate unleashed a slew of new storage products at last month’s CES show, including Maxtor BlackArmor drives, which are portable units with AES encryption, and Central Axis software, which provides secure remote access and file sharing for Maxtor Shared Storage II network drives.

The 2.5-inch, 160GB BlackArmor drives include NIST-certified encryption for security. A related feature is SeagateSecure technology, which keeps content locked up in case the drive is lost or stolen. BlackArmor drives are slated for availability in the second quarter, at a retail price of about $150, and Central Axis software will be available next month as a free download.

The latest addition to Seagate’s lineup of 2.5-inch drives for notebooks/laptops is the Momentus 5400.4, a 5,400rpm device with two platters, a 3Gbps SATA interface, and PMR technology.

Toshiba’s Storage Device Division (SDD) introduced at last month’s CES show a 320GB addition to its lineup of 2.5-inch drives, which also includes 250GB and 160GB models. The external USB 2.0 drives are bundled with NTI Shadow backup software.

Toshiba also announced plans to ship 1.8-inch external drives with capacities of 60GB, 80GB, and 120GB, as well as encryption and bundled backup software. The 1.8-inch drives are due in the spring time frame. -InfoStor staff