System StorageData can be held in 3 non-volatile ways

1) Magnetic Storage

2) Optical

3) Flash

Method 1) Magnetic This method uses Magnetic disks and are either fixed or removable. Examples of fixed

are Hard Drive and removable are Floppy Disks

Method 2) Optical Drives This methods uses a laser to read a write data. Examples include CD/DVD

Method 3) Flash Memory This method uses Flash memory . Examples include USB thumb drives and

SSDs

Non-Volatile StorageNon-Volatile storage does not lose data stored on it when the power is removed

Its usually cheap and slow

Hard Disk Drives (HDD)Hard Drives are a incredibly efficient computer memory device that

uses simple magnetism to store vast amounts of information

Hard Drives use spinning magnetic disks which the data (1 and 0) is stored on

This data is read and written by a mechanical arms which as the disk spins moves across the disk

1.Actuator that moves the read-write arm. In older hard drives, the actuators

were stepper motors. In most modern hard drives, voice coils are used instead.

As their name suggests, these are simple electromagnets, working rather like the

moving coils that make sounds in loudspeakers. They position the read-write arm

more quickly, precisely, and reliably than stepper motors and are less sensitive to

problems such as temperature variations.

2.Read-write arm swings read-write head back and forth across platter.

3.Central spindle allows platter to rotate at high speed.

4.Magnetic platter stores information in binary form.

5.Plug connections link hard drive to circuit board in personal computer.

6.Read-write head is a tiny magnet on the end of the read-write arm.

7.Circuit board on underside controls the flow of data to and from the platter.

8.Flexible connector carries data from circuit board to read-write head and platter.

9.Small spindle allows read-write arm to swing across platter.

Hard Disk Drives (HDD)

The data is stored in a very orderly pattern on each platter. Bits of data are arranged in concentric, circular paths called tracks. Each track is broken up into smaller areas called sectors. Part of the hard drive stores a map of sectors that have already been used up and others that are still free. (In Windows, this map is called the File Allocation Table or FAT.) When the computer wants to store new information, it takes a look at the map to find some free sectors. Then it instructs the read-write head to move across the platter to exactly the right location and store the data there. To read information, the same process runs in reverse.

File Systems

• Formatting installs a file system onto the partition.

• File Systems are a method of organizing your files and folders onto the hard drive.

• The File system tell the operating system where items are held so it can find them

• Think of a filing cabinet. File are arranged in a specific order with indicator to each section.

File Systems

Operating system File system(s)

DOS FAT16

Windows 95/98 FAT16, FAT32

Windows NT FAT16, NTFS

Windows 2000/XP FAT16, FAT32, NTFS

Windows 7 NTFS, FAT32

Windows 8/10 ReFS (Resilient File System), NTFS and FAT32

Hard Drives Issues

Fragmentation

Disk fragmentation is a result of how a computer uses storage on a hard drive. As time goes on, files on a hard disk drive will most certainly start to fragment. When a file is 'fragmented', parts of it are stored at various locations on a hard disk drive. The end result is that in order to access a file, a computer needs to access different parts of a hard disk drive. Because of the mechanical nature of a hard disk drive, the need to access different parts can dramatically slow down the overall performance

A Fragmented Hard Disk Drive showing files beingSpread all over the Hard Disk File

The picture to the left illustrates what a fragmented disk would look like when files that belong together are saved to different areas of the hard drive. The picture to the right illustrates what a disk would look like when the files that belong together are defragmented using a defragmenting software application.

A fragmented file does not lose any data, nor is it unreliable or insecure. In other words, fragmentation does not cause any serious problems. On the other hand, when a computer accesses a fragmented file, it takes longer than accessing one that is not fragmented.

Hard Drives Issues

What problems could a mechanical hard drive have?• Bad Sectors - A area of the hard disk drive that cannot hold data reliably because of damage or error. Caused

by bumping or banging the disk

• Lost Cluster - A lost cluster is a cluster that the operating system has classed as being in use, but actually contains no data. - The Scan Disk utility within Windows is designed to search for lost clusters and make them available to the file system again.

PartitioningPartitioning is the process of electronically subdividing the physical hard drive into groups of cylinders called partitions.

A hard drive must have at least one partition, but may have many.

Each partition is assigned a drive letter. i.e. C: or D:

Primary Partitions = Bootable (Must be set Active).Extended Partitions = Non Bootable (Contain Logical Drives).

Partitioning

Solid State Drive (SSD)

An SSD does not have a Disk to read and write data, it instead relies on an embedded processor called a controller to perform operations related to reading and writing data. They are very similar to a USB flash drive.

RAIDRedundant Array of Independent Disks.

A System that employs two or more drives in combination for fault tolerance, performance or both.

RAID provides a method of accessing multiple individual disks as if the array were one larger disk.

RAID either spreads or duplicates the data across multiple disks, thereby either improving access time or reducing the risk of losing all data if one drive fails.

Typically RAID is used in large file servers, and application servers, where data accessibility is critical, and fault tolerance is required.

There are number of different RAID levels.

Investigate the RAID Layers

Buying a Hard DriveCapacity

How much data the Hard Drive can store, usually in Gigabytes or Terabytes

Cache

Random Access Memory (RAM) that stores copies of frequently used disk sectors in so they can be read without accessing the slower disk

Read/Write Speed

The read speed is how long it takes to read something from the drive -- so, how long it takes to open a file that’s stored on the drive.

The write speed is how long it takes to save something on to the drive.

Interface

The connector the hard drive uses to communicate with the motherboard usually SATA or IDE

Form Factor

The size of the disk. 2.5" (small for laptops) or 3.5“ (Desktop Size)

• Types (HDD/SDD/Hybrid)

• Physical Size

• Connections (IDE/SATA/SCSI)

• Storage Capacity

• Transfer speeds

• Cache space

• Access times

Assessment Help – Storage