4. 6A-4
Describing Storage Devices
• Storage terms
– Media is the material storing data
– Storage devices manage the media
– Magnetic devices use a magnet
– Optical devices use lasers
– Solid-state devices have physical switches
(microchips/ NAND-based flash memory)
5. 6A-5
Magnetic Storage Devices
• Most common form of storage
• Hard drives, floppy drives, tape
• All magnetic drives work the same
6. 6A-6
Magnetic Storage Devices
• Data organization
– Disks must be formatted before use
– Format draws tracks on the disk
– Tracks are divided into sectors
• Amount of data a drive can read
– Each sector contains 512 Bytes (Floppy)
7. 6A-7
Tracks and Sectors
Floppy Disk Example:
Tracks: 80
Sectors: 18 (cuts every track like a pie)
Total Sectors: 80 X 18 = 1440 per side
Data is written on both side of the floppy disk
Total Sectors: 1440 X 2 sides = 2880
1 Sector contains 512 Bytes of data
Capacity of a Floppy: 2880 X 512 Byte (or 0.5 KB) = 1440 KB = 1.44 MB
8. 6A-8
Magnetic Storage Devices
• Finding data on disk
– Each track and sector is labeled
• Some are reserved
– Listing of where files are stored
• File Allocation Table (FAT)
• FAT32
• NTFS
– Data is organized in clusters
• Size of data the OS handles
9. 6A-9
Magnetic Storage Devices
• Diskettes
– Also known as floppy disks
– Read with a disk drive
– Mylar disk
– Spin at 300 RPM
– Takes .2 second to find data
– 3 ½ floppy disk holds 1.44 MB
10. 6A-10
Magnetic Storage Devices
• Hard disks
– Primary storage device in a computer
– 2 or more aluminum platters
– Each platter has 2 sides
– Spin between 5,400 to 15,000 RPM
– Data found in 9.5 ms or less
– Drive capacity reached 10 TB
11. 6A-11
USB Pen Drive
1 USB connector
2 USB mass storage controller device
3 Test points
4 Flash memory chip
5 Crystal oscillator
6 LED
7 Write-protect switch
8 Space for second flash memory chip
12. 6A-12
Solid State Devices
• Solid-state disks
– Extremely fast
– Non-Volatile storage
– Data is stored physically
– No magnets or laser
– No Disk or motor
13. 6A-13
Drive Performance
• Average access time
– Also known as seek time
– Time to find desired data
– Measured in milliseconds
– Depends on two factors
• RPM
• Time to access a track
– Hard drive between 6 and 12 ms
– CD between 80 and 800 ms
14. 6A-14
Drive Performance
• Data transfer rate
– How fast data can be read
– Measured in Bps or bps
– Hard drive ranges from 15 to 160 MBps
– CD ROMS depend on X factor
• 24x CD transfers 24 x 150 KBps
– Floppy disks transfer at 45 KBps
16. Interface Type Hard Drive SATA SSD NVMe SSD
SATA-III SATA-III PCIe Gen 3.0 x4,
NVMe 1.3
Read/Write Speeds Around 130 MB/s Around 500 MB/s 3,500 MB/s
IOPS (input/output
operations per
second)
Up to 100 IOPS Up to 100,000 IOPS Up to 500,000 IOPS
Reliability (MTBF) About 50,000 Hours 1.5 Million Hours 1.5 Million Hours
Available Capacities 500GB - 12TB 250GB - 4TB 250GB - 2TB
Average 500GB
Drive Price
$40.00 $65.00 $100
6A-16
SATA = Serial Advanced Technology Attachment
NVMe = Non-Volatile Memory Express
M.2 is Form Factor
