2. STORAGE DEVICES
HARD DISK DRIVE
STRUCTURE
PLATTERS
A platter is a physical object (actually, a plate) that resides inside the hard
disk and is responsible for storing the data.
READ/WRITE HEAD
When information is written to the disk, the read/write head will move to
the same track on all platters in a single movement and then write to the same
track on all platters. The actuator arm has multiple read/write heads on it.
ACTUATOR ARM
3. TRACKS
Just as there are grooves, or tracks, on a record or music CD, there are also
tracks on each platter. These tracks are evenly spaced across the platter’s surface.
SECTORS
The platter is divided into pie slices, thus dividing the tracks into 512-byte
sectors. Sectors are the actual storage areas for data, and each has an address that is
made up of the platter side number, the track number, and the sector number on
that track.
CLUSTER
A group of any number of sectors can make up a cluster. When a partition is
formatted, the file system will determine the cluster size based off the partition
size. For example, a partition that is 2GB in size formatted as FAT will use a 32K-
cluster size. That same 2GB partition formatted as FAT32 will use only a 4K-cluster
size
4. CYLINDER
A cylinder consists of the same track on both sides of all the platters. In
other words, when you reference Track 0, you reference a particular track on a
particular platter, but when you reference Cylinder 0, you reference Track 0 on
all platters.
If you know the number of cylinders, heads, and sectors per track, you
can calculate the size of a disk. For example, if you have a drive that has 4,092
cylinders, 16 heads, and 63 sectors per track, the size of the disk would be
2,111,864,832 bytes (2.1GB). The formula to calculate the size of the disk is
Cylinders × Heads × Sectors × 512 bytes per sector.
READ/RIGHT PROCESS
PERFORMANCE
Disk performance can be measured in terms of several important
characteristics: seek time, latency, access time, and the spin speed of the disk.
5. SEEK TIME
is the time it takes to move the read/write heads to the desired track. Seek
time is a calculated average, since the time it takes to move to the desired track will
differ from one instance to another. For example, if the read/write heads are on
Track 1, they will take a longer amount of time moving to Track 12 than to Track 3.
LATENCY
is the time it takes for the appropriate sector to move under the read/write
head.
SPIN SPEED
is the speed at which the platters spin in a circle
6. MASTER BOOT RECORD
is the 512-byte boot sector that is the first sector of a partitioned data
storage device such as a hard disk. MBR holds the following information
Holding a disk's primary partition table.[2]
Bootstrapping operating systems, after the computer's BIOS passes
execution to machine code instructions contained within the MBR.
7. (IDE)PATA
2 devices per controller (master / slave)
40-pin cable
ATAPI supports CD/DVD/Tape drives
Interface Maximum
DMA Mode Special Features
Standard Transfer Rate
ATA/ATAPI-4 UDMA 0, 1, 2 33 MBps Ultra DMA, 80
(UDMA-33) conductor cable and
CRC
ATA/ATAPI-5 UDMA 3, 4 66 MBps
(UDMA-66)
ATA/ATAPI-6 UDMA 5 100 MBps 48-bit LBA expansion,
(UDMA-100) and disk noise
reduction
ATA/ATAPI-7 UDMA 6 133 MBps Multimedia streaming,
(UDMA-133) SATA 1.0
9. CABLE ORIENTATION
ATAPI
is an interface standard for the connection of storage devices such as
hard disks, solid-state drives, and CD-ROM drives in computers.
SMART
is a monitoring system for computer hard disks to detect and
report on various indicators of reliability, in the hope of anticipating
failures.
10. SATA
sata supported speeds up to 150 MBps
Latest version (sata-3.0) supports speed up to 300 MBps.
External cabling (2 meter or 6 feet)
HOT SWAPPING
JUMPER
Jumpers allow the computer to close an electrical circuit allowing the
electricity to flow throughout certain sections of the circuit board. Generally,
the jumpers consist of a set small pins which can be covered with a small plastic
box. This box connects the two pins together allowing the electricity to flow
freely between the two pins.
11. SCSI
Is an expansion bus technology for connecting internal and external
devices. SCSI is commonly used for hard drives, especially in server level
systems.
Interface Bus speed Bus Max Cable Length (m) Devices
Protocol MBps Max Width per Bus
(bits) Single-ended LVD HVD
SCSI-1 5 8 6 12 25 8
Fast SCSI 10 8 3 12 25 8
Fast-Wide SCSI 20 16 3 12 25 16
Ultra SCSI 20 8 1.5 12 25 8
Wide Ultra SCSI 40 16 - 12 25 16
Ultra2 SCSI 40 8 - 12 25 8
Wide Ultra2 80 16 - 12 25 16
SCSI
Ultra3 SCSI 160 16 - 12 - 16
(Ultra160 SCSI)
Ultr320 SCSI 320 16 - 12 - 16
12. FLOPPY DISK DRIVE
PHYSICAL SIZE & CAPACITY:-
5.25” (360 KB, 512 KB, 1.22MB)
3.5” (1.22MB, 1.44 MB, 2.8MB)
INTERFACE :- Maximum support 2 device per MOBO.
RPM :-
OPTICAL DISK STORAGE
CD WORM
CD-R
Has a chemical die layer , typically silver alloy or 24 carat gold, used to carry
data bits; used to use aluminum as reflective layer.
13. FLASH MEMORY
Is a Non-volatile memory used in digital cameras, mobile phones, and mp3
players etc.
Some popular manufacturers are Smart Media, Compact Flash(CF), Secure
Digital(SD), Sony, and xD picture card.
USB thumb drive also use flash memory stick.
To remove the device you should use the Safely Remove Hardware routine.
14. TAPE DRIVES
Used to creating system backups, may be external or internal units.
Supplied with ATA/EIDE, SCSI, USB or Firewire interfaces.
TYPES
QIC:- Oldest type format can store up to 4 GB.
TRAVAN:- Can store up to 10 GB data.
DAT:- Can store up to 36 GB data.
8 MM TAPE SYSTEM:- Offers high capacity data storage up to 200GB
DLT(DIGITAL):- Developed for high speed lan based backup system
