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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….