Wednesday, January 4, 2012

Storage Devices


Storage Device Facts

When selecting a storage solution, first consider the type of storage device. The following table compares various storage devices.
Device Type Description
Hard disk Some of the advantages of hard disks are:
  • They have lots of storage (usually more than 100 gigabytes, whereas most floppies have a maximum storage capacity of 1.4 megabytes).
  • They are significantly faster than floppy disks.
  • The cost per MB (or GB) is cheap.
Some of the disadvantages of hard disks are:
  • Many hard disks are internal devices, though you can get external enclosures.
  • They are prone to failure.
  • They are sensitive to vibrations and drops.
  • They are vulnerable to magnetic interference.
Optical discs Optical discs such as CDs and DVDs are a storage medium that use lasers for both reading and writing information. Some of the advantages of optical discs are:
  • They are great for music and video (they play in audio or video devices that aren't computers).
  • They are portable and universal.
  • They are cheap.
  • You can buy CDs that are recordable.
  • They have a long shelf life and are relatively sturdy.
Some of the disadvantages of optical discs are:
  • They are slower than hard disks.
  • They have a small capacity (650 MB for audio CDs, 4.7 GB for DVDs, 25 GB for Blu-ray).
  • There are some compatibility issues between disc formats and readers.
Flash devices Flash devices store information using programmable, non-volatile flash memory. Common flash devices are MMC, SD, memory sticks, and USB thumb drives. Some of the advantages of flash devices are:
  • They can retain content without power.
  • They are optimal for use in devices like cameras.
  • They are highly portable.
  • They have a larger capacity than floppy disks and CDs. Some have even more capacity than DVDs.
  • They have relatively fast memory access.
Some of the disadvantages of flash devices are:
  • Their storage capacity is not yet comparable to the capacity of hard disks.
  • Different card formats require different readers.
Solid state drives (SSD) A solid state drive is a flash device with a storage capacity similar to a small hard drive. Solid state drives are used as replacements for hard disk drives for storing operating system, application, and data files. Some advantages of solid state drives:
  • They are faster than hard drives
  • They have no moving parts so they last longer
  • They have lower power consumption than hard drives (good for laptops)
  • They are less susceptible to physical damage (from dropping) and immune from magnetic fields
  • They are smaller and lighter than hard drives
The main disadvantage currently for solid state drives is cost--they are several times more expensive than comparable hard drives. However, their advantages make them a good choice, especially for portable devices.
After you have selected the type of storage device, you might have a choice to make regarding the interface type. The following table describes the most common storage device interfaces:
Interface Description
PATA PATA (also called EIDE, IDE, and ATAPI) is a parallel ATA interface. ATA is the standard interface for transferring data from storage devices such as hard disk drives and CD-ROM drives. PATA:
  • Is the most common and the least expensive interface for hard disks and CD/DVD drives.
  • Allows two devices per channel. Most motherboards include two built-in channels.
  • Use parallel communication (meaning devices share the same data transfer channel).
Some disadvantages of PATA interfaces are:
  • They have a maximum speed of 133 MB/s.
  • Because both devices share the same channel, devices must be configured properly to avoid conflicts.
  • They are being phased out and replaced.
SATA Serial ATA is computer bus technology primarily designed for transfer of data from a hard disk. SATA:
  • Is the successor to PATA.
  • Uses serial communication (meaning each device is on its own channel).
  • Is faster than PATA.
  • Provides built-in support for disk protection methods.
  • Provides for easy configuration--just connect the device to the SATA port.
  • Supports external devices through the External SATA (also called eSATA) standard. eSATA is faster than USB and Firewire.
USB/Firewire You can connect storage devices through the USB and Firewire buses. Storage devices that can be connected to the USB or Firewire bus include:
  • External hard drives and CD-ROM drives.
  • Internal hard drives in an external enclosure. These devices use a PATA or SATA drive in an enclosure that then connects to the system through USB or Firewire. However, an eSATA device connected to a SATA bus is faster than using an SATA drive in an external USB or Firewire enclosure.
  • Flash memory card readers.
USB and Firewire devices are highly portable and easy to connect.

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