Storage

What is storage?• Storage holds data, instructions, and information for

future use.• Storage medium is physical material used for storage.

Storage Media Types• Hard Disk.• Floppy Disk.• Zip Disk.• CD/DVD.• SD Card• Flash Memory.• Solid State Drive

Storage Medium Capacity• Number of bytes a storage medium can

hold• Nybble or Nyble 4 Bits• Byte 8 Bits• Kilobyte (KB) 1024 bytes• Megabyte (MB) 1024 KB• Gigabyte (GB) 1024 MB• Terabyte (TB) 1024 GB• Petabyte (PB) 1024 TB• Exabyte (EB) 1024 PB• Zettabyte (ZB) 1024 EB• Yottabyte (YB) 1024 ZB

Storage Device

Hardware that

records data

Writesitems from memory to

storage media

Readsitems from

storage media to memory

Drive Types

Hard Disk Drive (HDD)

Solid State Drive (SSD)

What is a Hard Disk Drive ?• It was invented in 1954 by IBM.• High capacity storage.• Consists of several inflexible,

circular platters that store items electronically.

• Components enclosed in airtight, sealed case for protection.

• The operating system, software and most other files are stored in the HDD.

Hard Disk Drive Interfaces• Parallel Advance Technology Attachment (PATA).• Small Computer System Interface (SCSI).• Serial AT Attachment (SATA).• Serial Attached SCSI (SAS).

Parallel Advance Technology Attachment (PATA)

• It has a 40 Pins Data Connector.• It has 4 Pins Power connector.• Data transfer rate is 133.3 MB/S.• If you have two devices connected to one IDE

controller, one must be set master and the other must be set to slave using jumpers and IDE cable.

• Max of two drives per controller.• Developed by Western Digital under the name

Integrated Drive Electronics (IDE).

Small Computer System Interface (SCSI)

• SCSI are high performance storage drives.

• SCSI drives are commonly found in servers were real time performance or 24/7 operation is required.

• It has 40 Pins Data Connector and 4 Pins Power connector.

• Data transfer rate is 320 MB/S for SCSI-3 Wide Ultra3.

• Max of 15/16 drives per controller.

SATA Drive Interface

• It is the latest high speed type of hard drive connectors.

• It has a 7 pin Data connector.• It has 15 pin Power connector.• Data transfer rate is

22.5 GB/S for SATA V4 at 2017• Max of 15 with a port multiplier.

The Serial Attached SCSI (SAS)

• It has a 7 pin Data connector.• It has 15 pin Power connector.• Data transfer rate is 6 GB/S • Max of 8 drives per controller.

Basic components of a hard drive

• Disk platters.• Read/write heads.• Spindle motor.• Stepper motor.• Logic board.• Cables & connectors.• Configuration items (such as jumpers &switches).

Hard Disk Platters• 3 1/2 inch drives are the most popular for desktop

& some portables.• Max number of platters in a 3 1/2 inch drive is 11.• Traditionally made from a magnetic material, in

the flat disk part of the drive.• The data stored in the platter.• Desire for higher density has led to the use of

platters made of glass (glass ceramic composite).  Glass platters offer greater rigidity & mores table thermally.

Read/Write Heads• A hard disk has one read/write head for each side of the platter. • The heads are connected on a single movement mechanism.• They move in same manner and direction.• Each head is on an actuator arm that is spring-loaded to force the

head into contact with a platter .•  The heads float only a very slight distance above the platter .• When the drive is at rest, the heads are forced into direct contact

with the platters by spring tension.

Spindle motor

• Motor that spins the platters.• Connected directly to the drive.• This motor rotates at a speed of

3600 to 15,000 RPM.• All the platter moves in the

same direction.

Stepper motor

• Use stepper motors for controlling read/write head position.• Stepper motors usually

use +12V power, but some new low-power drives use +5V power source.

Logic Boards

• Mounted on the hard drive.

• Contain electronics that control the drive’s spindle, head actuator systems, and present the data to the controller.

Cables & Connectors

• Connectors for interfacing to the computer, receiving power.

• Data cables: SATA cable. SCSI cable. IDE cable. SAS cable.

Disk structures

A:TrackB:Geometrical sectorC:Track sectorD:Cluster

• Track : The HDD is divided into number of concentric circulars called tracks.• Sector: Data storage area in one track multiple divided into

the multiple block. Each sector can have 512 bytes of the data.• Cylinder: A set corresponding tracks in all sides of a hard disk.• Storage capacity: its having a formula show below:

Storage capacity= number of cylinder's * tracks per cylinder *sector per tracks * bytes per sector.

Disk structures

HDD Problems

• No operating system.• Disk boot Failure (cable problem) OR (HDD Not Detect).

Solid State Drive

• It was invented in 1995 by M-systems.

• It’s a data storage device that uses solid state memory to store persistent data.

• SSDs use NAND based flash memory or DRAM to store data.

• The SSD need external power supply or battery pack.

Advantages DisadvantagesHigh performance They are more expensive

than traditional hard drive

Faster than a standard HDD

They currently offer less storage space than traditional hard drive

Faster seek time upto 60* faster than HDDLower powerSilent operation Lighter weightWider operating temp 0c- 70c

Hard Disk Drive Solid State DriveRandom access time 5 -10 M/S

Random access time 0.1 M/S

Read latency time high Read latency time very low

Low Reliability High ReliabilityHDDs have moving parts SSDs have no moving

parts Relatively large and heavy

Small and light in weight

In 2020 HDDs were available in size up to 40 TB

In 2018 SSDs were available in size up to 128 TB

Power consumption 12 watts

Power consumption 2 watts

RAID 0

• Minimum 2 disks.• Excellent performance (as blocks

are striped).• No redundancy (no mirror, no

parity).• Don’t use this for any critical

system.

RAID 1

• Minimum 2 disks.• Good performance (no striping. no

parity).• Excellent redundancy (as blocks

are mirrored).

RAID 5• Minimum 3 disks.• Good performance (as blocks

are striped).• Good redundancy (distributed

parity).• Best cost effective option

providing both performance and redundancy. Use this for DB that is heavily read oriented. Write operations will be slow.

RAID 1+0• Minimum 4 disks.• This is also called as “stripe of

mirrors”.• Excellent redundancy (as blocks

are mirrored).• Excellent performance (as blocks

are striped).• If you can afford the dollar, this

is the BEST option for any mission critical.

Thanks for your attention