7 - Indira Gandhi Centre for Atomic Research

These storage intensive applications have raised unprecedented demands on the current
storage infrastructure, which has been unable to keep up with the demand. If the
information demand is not handled adequately, this may result in information spill over,
server crash and the loss of important and confidential data.
3. Storage devices
Secondary storage is designed to store very large amount of data for extended periods of
time. These secondary storage devices can have memory capacity of Gigabytes or
Terabytes. The important characteristics of the secondary storage devices are:
• it is nonvolatile
• it takes much more time to retrieve data from secondary storage than it does form
RAM
• it is much more cost effective than primary storage
• it can be placed on a variety of media, each with its own technology
3.1 Magnetic tape
Magnetic tape is a cheaper storage medium and can handle enormous amount of data. The
downside is that it is the slowest for retrieval of data, because all the data are placed
sequentially. Sequential access means that the system might have to run through the
majority of the tape. Magnetic tape storage often is used for information that an
organization must maintain, but uses rarely or does not need immediate access. Industries
with huge number of files use magnetic tape systems. Modern version of the magnetic tape
systems use cartridge and often a robotic system that selects and loads the appropriate
cartridge automatically. There are also some tape systems like digital audio tapes, for
smaller applications such as storing copies of all content of personal computer’s secondary
storage ( backing up the storage ).
3.2 Magnetic disks
Magnetic disks are very popular because they are built in our portable or Personal
Computers Systems as a storage media. Also they allow much more rapid access to the
data than does magnetic tape. In a magnetic disk data can be accessed directly. The Hard
Drives in the system use stacks of rigid magnetic disks (hard disks). Hard disk provides
several GB of data storage to our personal computers. Data access in hard disk is very fast,
measured in milliseconds. For these reasons hard disks are extremely popular and
common.
3.3 Hard drive
Organizations also use hard drive systems for backup and long term storage. A common
technology is the Redundant Arrays of Inexpensive Disk (RAID). These machines use a
large number of small hard disk drives. The data are distributed across all of the disk
drives. The logic is that if one drive fails, the impact is greatly lessened. The access speed
of RAID makes it more appropriate than magnetic tape storage if the data are to be
accessed more often or require more rapid retrieval.
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