Hybrid drive

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A hybrid drive, a.k.a. Hybrid Hard Drive (HHD), is a new type of large-buffer computer hard disk drive. It is different from standard hard drives in that it employs a large buffer (up to 1 GB) of non-volatile flash memory to cache data during normal use. By primarily using this large buffer for non-volatile data storage, the platters of the hard drive are at rest almost all of the time, instead of constantly spinning as they are in current hard drives. This offers numerous benefits, chief among them speed,[1] decreased power consumption, improved reliability, and a faster boot process.

Hybrid drives are set to be released, primarily for notebook computers, in early 2007, with Samsung introducing their first drives in January, and Seagate in the first three months. At the moment, they are only known to be fully compatible with the Windows Vista operating system[2]; Microsoft uses the name ReadyDrive to describe the software side of this technology.

The command interface will be standardized in the new revision 8 of the ATA standard.

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[edit] Function explanation

Unlike most standard hard drives, the hybrid drive in its normal state has its platters at rest, as if it were off. During this time, any data that the user must write to the hard drive is written instead to the buffer. While working on a text document, for example, or browsing through the Internet, any temporary save files or the browser's disk cache will be saved to the buffer, instead of being written to the hard drive every time.

The hybrid drive's platters will spin up in only two situations. When the buffer begins to near its capacity, the platters of the hard drive will spin up, and all of the data in the buffer will be cleared onto the hard drive, whereupon the platters will again return to an off state, and the cache will be empty for use again. The second instance is when the user must access a new file from the hard drive that is not already stored in the buffer. In this case, the platters must spin up to access the file and place it onto the buffer, whereupon the platters will once again return to an off state.[citation needed]

Because the hybrid drive utilizes nonvolatile flash memory (such as those in a USB key), as opposed to volatile memory (such as RAM), the buffer is able to retain all the data even in the event of a sudden power failure or reboot, and can even store boot-up data into the buffer (see below).

Early estimates place the actual hard drive usage (when the platters are spinning) at anywhere between 1.25%[3] and 10%[4] for normal users, although there are obviously situations where hard drive usage will be much higher, such as the encoding or editing of very large video files. See flash memory for more disadvantages.

[edit] Benefits

The hybrid drive is claimed to offer several benefits over the standard hard drive, especially for use in notebook computers.

  • Decreased Power Consumption: Because the platters will almost always be in an off state, power consumption by the hard drive will be reduced. Although not so much of an issue for desktop computers, this greatly extends the battery life of notebook computers.
  • Decreased Heat Generation: The reduced spinning of the platters also greatly decreases the amount of heat generated, as few parts of the hard drive are physically moving (and generating friction).
  • Decreased Noise Levels: In addition to the decrease in noise due to needing less overall cooling because of decreased power consumption and heat generation, hybrid drives are almost completely silent due the decreased use of the hard drive platters.
  • Improved Reliability: As the platters won't be spinning nearly as much, the wear and tear on the hard drive is drastically reduced. Hybrid drives should be able to last much longer than today's standard notebook drives. In addition to this, head crashes — in which a sudden movement, such as a violent impact, causes the read/write head of the hard drive to physically impact one of the platters — will become much less frequent, as the head should be docked most of the time.[verification needed]

[edit] Drawbacks

There are also drawbacks to the use of hybrid drives:

  • Increased seek time for non-cached data: If the data being accessed is not in the cache and the drive has spun down, seek time will be greatly increased since the platters will need to spin up again.
  • Increased Cost: Flash memory chips are much more expensive per-gigabyte than comparably-sized traditional hard drives.
  • Increased frequency of spin-up: a hard drive, once spinning, suffers almost no wear. A significant proportion of wear arises during the spin-up and spin-down processes. A hybrid drive requires spin-up and spin-down more often than a normal hard drive, which is often spinning constantly.[citation needed]
    • Disk spinup is also the time when HDD uses the most power. [5]

Two other potential issues arise with regards to flash memory:

  • Lower recoverability - After failure any data in flash memory is completely lost as the cell is destroyed, while if normal HDD suffers mechanical failure the data is often recoverable using expert help. The amount of data lost if the cache of a hybrid drive is lost may be significant due to the cache size compared to the cache on non-hybrid drives.

[edit] See also

[edit] References

  1. ^ "Samsung says flash drive boosts speed of Windows Vista", Electronics Weekly, 26 July 2006. Retrieved on 2006-01-21.
  2. ^ Windows Vista is very power-intensive, even without using Aero [1], to the point that starting in June 2007 Microsoft will require the use of a hybrid hard disk for laptops to obtain the "Vista Premium" certification logo (in order to reduce overall power consumption and extends battery life) [2] [3][4] ...CORRECTION: NOT REQUIRED only min-specs if they are
  3. ^ Kanellos, Michael "Hybrid drive to extend notebook battery life" CNET News.com 26.04.2005
  4. ^ "Notebook Storage Gets Buffer" Maximum PC July 2005, pg. 15

[edit] External links

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