External Memory

A presentation on External memory from the "Computer Architecture" course.

1. External Memory

2. 2 Notre Dame University Bangladesh Submitted By: Rup Chowdhury – 201120010 Submitted To: Mostafiz Ahammed Lecturer, Department of CSE Notre Dame University Bangladesh

3. What is External Memory? 3 External  memory, also called "secondary memory" refers to a storage device that can retain or store data persistently. They could be embedded or removable storage devices.

4. Types of External Memory External Memory Magnetic Disk RAID Optical Memory Magnetic Tape

5. Magnetic Disk A disk is a circular platter constructed of nonmagnetic material called the substrate, coated with a magnetizable material. Traditionally the substrate used in a disk are Aluminum or Aluminum alloy material. But recently glass substrates are used in magnetic disk.

6. Benefits of glass substrate Improved surface uniformity Reduction in surface detects, so reduced read/write errors Lower flight heights Better Stiffness Better shock/damage resistance.

7. Read and Write Mechanisms Recording and retrieval done via conductive coil called a head. During read/write, head is stationary. Write Current through coil produces magnetic field Pulses sent to head Magnetic pattern recorded on surface below Read Magnetic field moving relative to coil produces current Coil is the same for read and write

8. RAID RAID (redundant array of independent disks) is a way of storing the same data in different places on multiple hard disks or solid-state drives (SSDs) to protect data in the case of a drive failure. There are different RAID levels, however, and not all have the goal of providing redundancy.

9. 9 Optical Memory These memories use light beams for its operations and require optical drives for its operations. These memories are used for storing audio/video, backup as well as caring for data. Read/write speed is slower compared to hard disk and flash memories.

10. 10 Magnetic Tape The magnetic tape is a layer of plastic coated with a magnetic documentation medium . Magnetic tapes are used in most organizations to save data files. Magnetic tapes use a read-write mechanism. The read-write mechanism defines writing data on or reading data from a magnetic tape.