Data Storage Unit3

7/30/2019 Data Storage Unit3

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Data Storage-Unit3Presented By:

Gourav Kumar Dubey


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Overview of the Presentation

Magnetic disk,

Magnetic tape, CD-ROM, WORM,

Optical disk,

Mirrored disk,

Fault tolerance,

Network protection devices,

Power Protection Devices like UPS,

Surge protectors.


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Magnetic Disk

The Most Commonly used & popular storage medium

for the direct access secondary storage.

Offers high storage capacity,reliability,& capability to

access the data directly.

Data is represented as magnetised spots on disk.

Data in the magnetic disks can be erased and reusedvirtually infinitely.


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Storage Organization & Access of Magnetic Disk

TheSurfaceofthedisksisdividedintotheimaginarytracks

andsectors.

Theintersectionthetrack&sectorsarecalledastheTrack

Sectors.

Accessing Data from the Magnetic Disk Seek

Rotate

DataTransfer

Seektime,latency&datatransfertimeisdefinedastheaccesstimeofthemagneticdisk.


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Types of Magnetic Disks

Floppy Disk

- Coated with the Ferric Oxide, & encased in aprotective plastic.Used for both read & write

operations.

Hard Disk

- also called as fixed disk, used as the primary storage

unit of the computer.

Zip Disk

- a removable storage device with the capacity of 100-

250 MB of data.its drive unit is measured as

18*13*4cm & weights upto Kg.


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Advantages & Disadvantages of Magnetic Disks

Follow direct access mode for both reading & writing

onto the data files.

Used for both as an online & offline storage.

Data transfer rate is much higher than the magnetic

tapes.

Less chances to the corruption of the data than MagneticTapes.

Disadvantages:

Must be stored in a dust-free environment. Expensive than magnetic tapes.

More suscpectible for the breach of security.


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Magnetic Tape

Its like a plastic tape with the magnetised coating on it.

Data is stored in the form of tiny segments of magnetised& demagnetised portion on the surface of the material.

Beginning of the tape(BOT) & End of the Tape(EOT) is

described as the usable recording (reading/writing)

purposes.

Very durable and can be erased as well as reused.

Cheap and reliable storage medium for archives & taking

Backups. Offers high storage capacity, reliability & capabilities to

access the stored data.


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Advantages & Disadvantages of the Magnetic Tapes:

Advantages:

Holds high recording data capacity, results as the low incosts.

Easily transportable because of their size & lightweight.

Disadvantages:

Data on these devices are difficult to recover, if a minor

bit of problem occurs.

Data Transmission is low in comparison to the magnetic

disks.

Data cannt be update as in the insertion/deletion forms.


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Optical Disk

A flat, circular, plastic disk coated with a thin layer of

metal (alluminium, gold, silver).

A reflective surface is used as a read/write head for the

recording data onto the disk.

Types of Optical Disks:

Compact Disk-Read Only Memory(CD-ROM)

Digital versatile/video Disk-Read Only Memory(DVD-

ROM) Write Once-Read Many(WORM)


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Compact Disk-Read Only Memory(CD-ROM)

Capable of being used as a data storage device along with

storing of digital-audio.

A CD-ROM disk is shiny, silver colour metal disk of 12

diameter.

Made

up of three layers:

Layer of alluminium, a layer of acrylic & with the

polycarbonate base. Files are stored on the contiguous sectors or tracks.


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Write onceRead Many (WORM)

It is a thin (1.2mm)disk madeup of

polycarbonate with a 120mm diameter, which ismainly used for storing the music or data.

Eg.CD-R(Compact-Disk Recordable).

Data can be written but cannt be erased on an

optical disk.

How actually Data is Stored..?

A laser actually burns Microscopic Pits into the

disks surface for the record of data.


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Advantages & Disadvantages of Optical Disks

Advantages:

Life span of data storage is more, about 10-20 years. Physically harder to break or melt.

Can store more data in less amount of space as compared

to the magnetic tapes & floppy or Zip disks.

Easily portable & stored due to their small size.

Disadvantages:

Complicated than the magnetic & Floppy disk.

Slow data access speed as compared to the magnetic

disks.

Much more costlier than the floppy & zip disks.


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Mirrored Disk

when applications require high reliability, it may

be appropriate to use a configuration that supports

mirrored disks. With this configuration , data is

automatically written to two disks.

Through mirroring it allows a system to

automatically maintain multiple copies of data to

the mirrored disk.

Helps us to continue the process or recover the

data from unwanted failure on system.


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Fault Tolerance Fault-tolerance or graceful degradation is the

property that enables a system (often computer-

based) to continue operating properly in the event of

the failure of (or one or more faults within) some of

its components.

Usually measured at the application level and not

just at a hardware level.

fault-tolerant systems can be characterised as either

roll-forward:system detects that it has made an

error,(or)

roll-back:operations between the checkpoint and

the detected erroneous state.

N k P i D i


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Network Protection Devices

Network Interface Card (NIC)

is a device that allows computers to be joinedtogether in a LAN(local area network).

Can be cabled or wireless (radio)

Often now built into motherboards.

Rated by speed: 10, 100, 1000Mbps.

Auto-sensing e.g. 10/100/1000 NICs adjust

themselves to the best possible speed.


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A system designed to prevent unauthorized access to or

from a private network. Firewalls can be implemented in

both hardware and software, or a combination of both.

To prevent unauthorized electronic access to a networked

computer system.

Types of firewall techniques: Packet filterPacket filtering is fairly effective and

transparent to users, but it is difficult to configure.

Application gateway: Applies security mechanisms to

specific applications, such as FTP

Circuit-level gateway: packets can flow between the

hosts without further checking.

Proxy server: hides the true network addresses.

P P t ti D i lik UPS


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Power Protection Devices like UPS

Uninterruptible Power Supply (UPS):

A device that provides battery backup when the electricalpower fails or drops to an unacceptable voltage level.

Used to protect Computers,DataCenters,Telecommunication

equipment or where can be an unexpected power disruption.

The world's largest UPS, the 46-megawatt, Battery Electric

Storage System (BESS), in Fairbanks, AK, powers the entire

city and nearby rural communities during outages.


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Surge Protectors A standard equipment which actually helps us to protect

our Computer Systems from voltage spikes.

The component Metal Oxide Varistor (MOV) diverts the

extra voltage.

It Consist of three Parts mainly:

A piece of metal oxide material in the middle, joined to thepower &

Grounding line by two semiconductors.

Most UPS systems include integrated surge protectors.

Surge protectors can also protect telephone and cable lines

as these also carry electric current.


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THANK

YOU

Data Storage Unit3

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