CMPTR Chapter 2 – Part 2 (Storage)

Storage – Punch Cards

Player Piano Roll

Punch Cards were used before disk drives.

Storage – Magnetic Disks

On magnetic media, such as floppy and hard disks, data is stored magnetically; the data (0s and 1s) is represented using different magnetic alignments.

3½” floppy 5¼” floppy

Inside a hard drive

Large Mainframe Hard Drives from 1970’s

Storage – Magnetic Disks

External USBHard Drive

Network Attached Storage (NAS)Connects to hub with networkcable so all computers on yournetwork can access it.

Hard drive for Macbook Air, laptopcomputer, and desktop computer. Newer Macbook Air’s have switchedto SSD drives.

Disks (both magnetic and optical) are Random or Direct access - the read/write head can move directly to the data.

Disk performance is measured by seek time (ms) and data transfer rate (MBps).

Disks may have cache RAM to speed up access time.

Network Storage and Online/Cloud Storage Systems

• Remote storage devices accessed via the Internet are often referred to as online storage or cloud storage.

– The disadvantage is that tape has sequential access (have to fast forward and rewind) as opposed to direct/random access for disks.

– The advantage is tape has a very low cost per megabyte of storage and is removable. Therefore, tape is mostly used for backup and archival purposes where slow data access time is not as important.

Storage – Magnetic Tape

Backup Terminology

Full Backup – All data on hard drive is backed up.

Incremental Backup – Only modified data (since last full backup) is backed up. An example backup plan for a server might be to do a full backup on Sunday night, and incremental backups Mon, Tue, Wed, Thur, and Fri nights.

Off-site Backup – data is stored at a remote location.

Historical Backup – data backup is stored for a long time or forever.

Storage – Magnetic Tape

CD formatsAudio Format was developed by Sony and Philipsin 1981 and could contain 74 minutes of music at asampling rate of 44.1 kHz.

CDFS is the standard format of a CD that containscomputer files and folders. MP3 CD’s are fileformatted CD’s with mp3 songs.

CD typesCD-ROM is pressed at the factory and can besingle/double sided, single/dual layer (80 min/700 MB).

CD-R can be recorded once.

CD-RW are rewritable. The instructor does notrecommend using these because of compatibilityissues.

Storage – Optical (CD)

Storage – Optical (DVD & BD)DVD types

DVD-ROM is pressed at the factory and can be single/double sided, single/dual layer (4.7 GB – 18.8 GB).

DVD-R, DVD+R can be recorded once and store 4.7 GB.

DVD-RW, DVD+RW are rewritable and store 4.7 GB.

DVD-R DL, DVD+R DL dual layer DVD’s can be recorded once and store 8.5 GB.

Blu-ray

BD (Blu-ray Disk) is a standard created by Sony. They store 25/50 GB (single/dual layer).

BD-R are recordable Blu-ray disks 25/50 GB (single/dual layer).

Storage – Flash Memory

SSDWhen flash memory is used in place of a hard disk drive, it is called an SSD (solid state drive). It is faster and uses less power than a hard disk drive.