Notes

Outline

Permanent Storage Types

Data Can Be Stored Short or Long Term Short term storage is in RAM RAM is Random Access Memory When the power goes off data in RAM is lost! This means we require other memory types for permanent storage. Permanent Storage is also generally cheaper than RAM. This means we can store more in Permanent Memory!

Hard Diskettes or Hard Drive Current Hard Drives use magnetic technology and have capacities of 20 Gigabytes or more for less than $200. Most Hard Drives for PC’s are EIDE, or Ultra2 EIDE’s. Also USB and Firewire Drives are available…removable! PCMCIA for laptops…pricey Most of the intelligence for the HD is on the Onboard Controller Some computers use SCSI hard drives and other SCSI devices RAID is a special type of redundant hard drive setup with multiple disks.

High Capacity Removable Disk Storage Used to shuttle large amounts of data between computers Can also be used as a backup media Capacities range from 35M to over 2G Cost of media varies depending on technology used

Common PC Removable Media Types SyQuest drives (over 1G data) Uses proprietary 3.5 and 5.25 inch cartridges Jaz drives (up to 2G data) Media rather pricey Tape drives (Over 25G data) De facto standard for backing up data (covered in detail later)

Types of Removable Media Drives Magnetic Media Zip Drive LS-120 Drive Optical Media (Magneto-Optical) CD-ROM CD/RW

Zip Drive Available as IDE, SCSI, USB or Parallel interfaces Stores up to 250 megs of data Proprietary standard Up to 1M/sec access time

LS-120 Drive Also known as “Super Disk” Can read and write to standard 1.44M floppy disks Can store up to 83 times (120 Megs) as much data as 1.44M floppy Uses IDE, Parallel or USB interfaces

What is a CD-ROM? 5 inch disk Holds up to 682Megs of data Up to 74 minutes of audio Are coated with aluminum Most popular media used for software distribution Optical storage media

CD-ROM Technology Data is written by etching pits into the surface of the disk Areas that are not pitted are called “lands” Light is beamed to the disk The reflection is interpreted by the processors as either data or sound

Performance Factors Drive speeds up to 100x (100 times faster than a standard audio CD) Rated drive speeds are actually maximum speeds Up to 21Mb/sec transfer rates Access rates up to 80ms

CD-ROM Drive Interfaces SCSI Best performance and flexibility IDE/ATAPI Most common interface. Good performance at a lower cost Parallel port Convenient and easy to install. Can be expensive PCMCIA/USB for Laptops

Writable CD-ROM Drives CD-R WORM (Write Once Read Many) drives Excellent for burning “Masters” of data or music CD-RW Can be rewritten at least one thousand times

DVD (Digital Versatile Disk) DVD-Video contains only video programs DVD-ROM used as a data storage medium for PCs Backwards compatible (will play CD-ROM and audio CDs)

DVD Specifications Single sided single layer holds up to 4.7G data Single sided dual-layer up to 8.5G data Double sided single layer up to 9.4G Double sided dual-layer up to 17G

Other CD Technologies Enhanced Music CDs Contains music and data. Sometimes called CD Plus or CD Extra PhotoCD Sold by Kodak as a photo archiving media Divx Short lived technology, already obsolete

Flash and Other New Storage Flash memory cards used in new technologies such as digital cameras Several Different types in use, no current standard Other methods on the horizon including molecular technology

Safeguarding Data-Backup Data The most expensive component on a business PC! Loss of Data can be a disaster! Backup means making an extra copy. Tape, duplicate Hard drives, or other means. Separate the back up physically! Tornadoes, Hurricanes, Floods, Fire & Theft!

Tape Storage Tape used to be very popular with larger computers because of cost and types of use Now since it is sequential and relatively slow it is used primarily as backup. Larger computers use larger tapes PC’s generally use smaller cartridges which are cheaper, but generally slower Tape is plastic with iron rust bonded on

Disk Drives First disk drives were 8 inches, then 5 ¼ inch in diameter Current Floppies are 3 ½ inch in diameter They hold 1.44 Megabytes of Data Zip diskettes hold 100 or 250 megabytes Super disks hold 100 megabytes and can read the old 3 ½ inch 1.44 Meg floppies.

Disk Characteristics Diskettes, both floppy and hard must be formatted before use. They consist of Tracks (a circular path around) and Sectors Hard disks have more tracks and sectors and are much faster. Some devices are much faster than others as noted by Seek time or data transfer rates.

Optical Technologies Since the invention and widespread use of the Laser, light can be used to read stored data. CD ROMS were the first optical devices used widely to store data.  Stores 650 Megs Uses pits to store data.. No reflection there. DVD ROMS, and CD R and RW now in use DVD can store up to 4.7-17 GIG’s of data

New Storage Flash memory cards used in new technologies such as digital cameras Other methods on the horizon!!!

Safeguarding Data-Backup Data The most expensive component on a business PC! Loss of Data can be a disaster! Backup means making an extra copy. Tape, duplicate Hard drives, or other means. Separate the back up physically! Tornadoes, Hurricanes, Floods, Fire & Theft!