STORAGES

Delan Zoe Hilado-Arenga, ECE

Storage

• Storage - the area where data can be left on a permanent basis while it is not needed for processing

• Examples of Storage devices– ROM chips (Read-Only

Memory)– magnetic disks– CD-ROM (Compact Disk

Read-Only Memory)– magnetic tapes

Choosing a Storage Technology

• Versatility: the ability of a storage device to access data from more than one type of storage media

• Durability: The ability of a storage medium to withstand damage or mishandling.– Optical storage is more durable than

magnetic storage• Capacity: The amount of data a

storage medium can store.

Choosing a Storage Technology• Speed

Access time: The average time it takes a computer to locate data on the storage medium. (measured in milliseconds)

Random access (direct access): The ability of a storage device to jump directly to the requested data.

Sequential access devices must read from the beginning to end in order (tape drive).

Data transfer rate: The amount of data that a storage device can move from the storage medium to the computer per second.

Magnetic and Optical Technologies

• Magnetic storage uses hard disk, floppy disk, and tape storage media and stores data by magnetized microscopic particles on the disk or tape surface.

• A read-write head mechanism in the disk drive reads and writes the magnetized particles that represent data.

• Optical storage uses CD and DVD storage media and stores data as microscopic light and dark spots on the disk surface.

• The dark spots are called pits and the light spots are called lands.

Hard Disk Technology• A hard disk platter is a flat,

rigid disk made of aluminum or glass and coated with a magnetic oxide.

• A hard disk consists of multiple hard disk platters.

• A hard drive mechanism includes a circuit board called a controller that positions the disk and read-write heads to locate data.

Disk drives are classified according to the type of controller:

Ultra ATA (fastest), EIDE, SCSI

Hard Disk Technology (cont.)

• Direct memory access (DMA) allows a computer to transfer data directly from a drive into RAM without using the processor.

– Ultra DMA (UDMA) is a faster version of DMA technology.

• A head crash occurs when a read-write head physically touches a disk platter.

• RAID (redundant array of independent disks) contains many disk platters, provides redundancy, achieves faster data access than standard hard disks.

Hard Disks Interface standards

• SCSI Small Computer Systems Interface.

• IDE Integrated/Intelligent Drive/Device Electronics.

• SATA Serial ATA or Serial Advanced Technology Attachment.

SATA interface

• much smaller cable • can be up to 1 meter in length • point-to-point solution • ability to hot-plug • up to 150 MBps from parallel ATA's

maximum theoretical speed of 133 MBps

SATA

How Data Files are Stored

TASK

• 3 Brands/Models Specifications

• IDE HDD• SATA HDD

– Desktop– Laptop– Netbook

Tape Storage Technology• A tape backup is a copy of the

data on the hard disk that is stored on magnetic tape and used to restore lost data.

• Data on a tape drive is arranged as essentially a long sequence of bits.

• Tape is not practical as a computer’s main storage device. However, for backing up data, it takes about 15-20 minutes to back up 1 GB of data.

Other Examples….

• OPEN REEL TAPES – large reels with 16 mm film and access time in seconds , seen in old movies

• TAPE CARTRIDGES – half-inch removable magnetic tape similar to cassette tapes

TAPE Recorder

• IBM 3607 2 U Rackmount LTO Tape Autoloader

• 80 MB/s• 16-cartridge tape • 3.2 TB³ of data storage in

compressed mode

Tape Backup

• One of the simplest and most versatile tape backup software in the world.

• Compatible with any tape format (DAT, DDS, DLT, SDLT, AIT, VXA, LTO, etc...)

• any tape drive interface (SCSI, IDE, USB, SAS, etc...).

Floppy Disk Technology• A floppy disk is a round piece of flexible

mylar plastic covered with a thin layer of magnetic oxide and sealed inside a protective casing.– A floppy disk can hold 1.44MB of data.

• A ZIP disk or a Superdisk can hold 100 to 750 MB of data (various sizes). 20 times more faster

• Disk density refers to the closeness and size of the magnetic particles on the disk surface. The higher the disk density, the smaller the magnetic particles.

• A floppy disk features a write-protect window which allows you to protect the data on the disk form erasing existing data or adding new data.

Floppy Disks Capacities

Floppy Disk Construction

TRACKS & SECTORS

& CLUSTERS

• To speed up the process of reading and writing of data, a disk drive handles a groups of sectors called “clusters”

• Depends on the capacity and the disk technical specifications.

CD Technology

• CD-ROM (compact disc read only memory) contains data that has been stamped on the disk surface when it was manufactured.

• Read only means that the computer can retrieve data from a CD-ROM but cannot save any new data on it or delete data from it.

• A CD-ROM can store up to 680MB of data.

CD-R & CD-RW Technologies

• CD-R (compact disc-recordable) . – The data on a CD-

R disk cannot be erased or modified once you have recorded it, but more data can be added until it is full.

• CD-RW (compact disc-rewritable) technology allows you to write data on a CD, then change that data.

DVD, DVD+RW Technologies• DVD (digital video

/versatile disc) is a variation of CD technology that is designed to provide enough storage capacity for a full-length movie. (4.7 GB or more)

• A DVD-ROM disk is stamped with data and cannot be changed.

• DVD+RW uses phase change technology very similar to CD-RWs.

• There are already computers with one device that can read CD-ROMs, DVD-ROMS, and write DVDs.

Adding Storage Devices

• The system unit case for a desktop computer contains several storage device “parking spaces” called drive bays.

• If you have an empty bay of the right type and size, you can add a storage device.

• Bays come in two widths:

– 5 ¼” and 3 ½”

Optical Storage•Pits – non-reflective dark spots

Land – lighter and non-pitted reflective surface areas of the disk

How…?

Designation SidesLayer

s(total)

Diameter

Capacity

(cm) (GB)

CD–ROM 74 min

SS SL 1 1 12 0.682

CD–ROM 80 min

SS SL 1 1 12 0.737

CD–ROM SS SL 1 1 8 0.194DDCD–ROM SS SL 1 1 12 1.364DDCD–ROM SS SL 1 1 8 0.387DVD–1 SS SL 1 1 8 1.46DVD–2 SS DL 1 2 8 2.66DVD–3 DS SL 2 2 8 2.92DVD–4 DS DL 2 4 8 5.32DVD–5 SS SL 1 1 12 4.70DVD–9 SS DL 1 2 12 8.54

Assignment

• Compare DAO,TAO,SAO & Packet Writing modes

TASK(1/4 Illustration Board)Label the Internal Parts of a flash diskand their usage

FILE ALLOCATION TABLES ( FAT)

NEXT MEETING….