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Hard disk drive technology trends

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Steadily evolving HDD technology will also force storage managers to revisit issues like encryption, compression and data deduplication. IT managers can now decide the best place to do encryption or deduplication: on the server, the array, an appliance or the disk drive. With the newest generation of HDDs, all options are on the table.

Similarly, new HDD technology offers more energy-saving options, primarily via disk spin-down technologies. But the massive amounts of capacity on a single drive also raise questions about the efficacy of RAID 5 as a data protection technique (see "The end of RAID," below).

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The end of RAID

For industry analyst Mike Karp, the growing capacity of multiple terabyte disk drives inevitably increases disk errors. "For every unit of capacity we know there will be a certain number of errors," he said.

Organizations traditionally relied on RAID 5 to overcome those errors through the use of parity data. However, because of the time it takes a system to rebuild a 1 TB drive using RAID 5 the likelihood that another drive may fail increases, compounding the problems. Karp's solution is object-based RAID, which relies on small units of storage and allows the system to rebuild the drive in smaller increments. Others suggest RAID variations that use multiple parity disks, such as RAID 6, can do the job. (See "Alternatives to RAID")

Price/Capacity curve

The data storage industry has enjoyed a long ride up the price/capacity curve. Each year vendors pack more data onto disks with a corresponding drop in the cost per gigabyte. It's the storage industry's version of Moore's Law.

In recent years, 40% annual price/capacity improvements have been typical, but that pleasant pace may be slowing. "It will be increasingly difficult to get these kinds of gains," said Mark Nossokoff, a senior member of the strategic planning team at LSI Corp.'s Engenio Storage Group. The latest gains resulted from the vertical stacking of bits on the disk to overcome the limits of the superparamagnetic effect. Future increases will need a new technology advance. Bit-patterned media (BPM), heat-assisted magnetic recording (HAMR) and microwave-assisted magnetic recording (MAMR) are the leading contenders to replace perpendicular technology (see "New technologies pack more data on disks," below).

New technologies pack more data on disks

Several technologies are vying to produce the next breakthrough in packing more bits on a piece of storage media. Currently, perpendicular magnetic recording (PMR), which stacks bits vertically on the surface rather than laid out horizontally, is the technology of choice, but it will hit the superparamagnetic limit within a few years. But alternative technologies are emerging, including:

  • Bit-patterned media (BPM) stores each bit as a nanometer-scale pattern of grains on the media. As described by Hitachi, it creates an ordered array of highly uniform islands, each island capable of storing an individual bit.
  • Heat-assisted magnetic recording (HAMR) uses heat to stabilize the tiny stored bits, allowing smaller bits to be recorded. HAMR, however, creates heat, which runs counter to the industry's growing green storage impulses.
  • Microwave-assisted magnetic recording (MAMR) writes bits at different layers of the media.

HAMR will likely be ready for production by 2013, with MAMR probably ready a year later, according to Mark Nossokoff, a senior member of the strategic planning team at LSI Corp.'s Engenio Storage Group.

This was first published in May 2010

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