Hard Drive Components 1.5 Install and configure storage devices and use appropriate media YT Video 3:30

The Hard Drive Top to bottom: 1", 1.8", 2.5", 3.5”, hard drives The hard drive is the primary long-term storage device used in personal computers Hard drives are not volatile-even without power data remains stored on the drive Hard drives come in three sizes for personal computers 3.5" size for desktops 2.5" size for laptop computers 1.8" size for low-end laptops and other equipment such as MP3 players

Hard drives come in 2 types Hard Drive Types Hard drives come in 2 types The most common type of hard drives with moving parts are known as hard disk drives (HDDs) The newer and expensive technology that has no moving parts are called solid state drives (SSDs) In addition, some drives use a combination of these 2 technologies and are known as hybrid drives

Magnetic Hard Drives HDDs are generally larger in capacity than a SSD A magnetic hard drive has a mixture of both physical and logical components The physical components of a hard drive include: Platters Read/write heads Actuator/actuator arms The logical components of a hard drive include: Tracks Sectors Clusters

Magnetic Hard Drives Physical Components Platters, or disks, can be written to on both sides Hard drives can have multiple platters, which are extremely smooth and cannot be exposed to outside air A tiny dust particle can cause damage to the drive Every platter requires 2 read/write heads, one on the top and one on the bottom (if a drive has 4 platters it needs 8 heads) Read/Write heads move across the platters as they rotate on a spindle The heads ride on a very thin cushion of air hundreds of times smaller than a human hair

Magnetic Hard Drives Physical Components The actuator controls the movement of the actuator arm The actuator arm moves back and forth around an central axis point (called the actuator axis) This allows the read/write head to be positioned on different areas of the platter Today hard drives use a voice coil motor to move the actuator arm

Magnetic Hard Drives Logical Components Each platter is logically divided into a thousand or more tracks, which are circular areas on the disk When the head is over a track, it can read or write data Tracks are logically divided into sectors and they are the smallest storage unit on a disk Sector markings are written to a magnetic drive before it leaves the factory in a process called low-level formatting A sector often stores 512 bytes but with new hard drives the sector size is moving to 4096 bytes (4K)

Magnetic Hard Drives Logical Components A cluster is a group of multiple sectors Files are written to a cluster, but if the file is bigger than a single cluster, it is written to multiple clusters In a perfect world a file will be written to clusters that are next to each other

Solid State Drives YT Video 4:05 A solid state drive (SSD) uses memory chips to store data instead of metal spinning parts SSDs are usually built using NAND flash memory which retains data when power is disconnected The lifespan of a SSD is based on the number of write operations to the drive SSDs are more expensive, but faster, more reliable, last longer, and use less power than HDDs

solid-state drives by Toshiba

Hard Drive Interface Standards Interface standards define data speeds and transfer methods within a system They also define types of cables and connectors Interfaces can be divided into 2 categories, internal and external standards External standards include eSATA, USB, Firewire, Thunderbolt, and SCSI Internal standards include PATA, SATA, and SCSI (pronounced scuzzy)

Internal PATA Drives PM (800 series) Video 8:09 Integrated Drive Electronics (IDE) appeared in the 1980s In the early 1990s IDE was standardized as ATA, later named ATA-1, and the maximum drive size was 137 GB In the mid 1990s enhancements of the original IDE were marketed as Extended IDE (EIDE) and later standardized as ATA-2 In the early 2000s ATA was upgraded to ATA-7, SATA was introduced, and EIDE was renamed to PATA to differentiate it from SATA Originally IDE and ATA were only for hard drives but ATA Packet Interface (ATAPI) provided standards so they could be used with optical drives (CD or DVD-ROM)

Timeline of interface standards used by internal drives

Summary of ATA interface standards

80-conductor cable and 40-conductor cable; they are about Internal PATA Drives Parallel ATA (PATA) sends data in parallel 80-conductor cable and 40-conductor cable; they are about the same width, but the 80-conductor cable has many more and finer wires Allows 1 or 2 connectors on a motherboard Allows 2 drives on a single cable (master/slave) PATA has been mostly replaced by SATA Types of PATA ribbon cables The first drives used a 40-pin cable 40 pins and 40 wires The cable has a colored strip down one side (Pin 1) ATA-5 defined the use of a new 80-conductor cable (blue connector) 40 pins and 80 wires Maximum recommended length of either is 18”

Internal SATA Drives PM (800 series) Video 4:03 Serial ATA standards use a serial data path rather than the traditional parallel data path used by PATA drives Some advantages SATA has over PATA include: SPEED: SATA is faster than PATA and is used by all drive types NO MASTER/SLAVE: Multiple connectors are easier to configure with no master or slave configurations needed HOT SWAPPING: SATA supports hot-swapping (hot-plugging) Connect and disconnect drive while system is running CABLE LENGTH: The SATA maximum cable length of 40 inches is more than twice that of a PATA cable length AIRFLOW: SATA cables don’t hinder airflow (narrower than PATA) A SATA data cable and SATA power cable

SATA standards

Internal & External SCSI PM (800 series) Video 9:35 Small Computer System Interface (SCSI) has been around a long time While it has provided better performance than PATA drives it is more expensive and harder to implement With the popularity of SATA drives, SCSI drives are largely falling out of use SCSI is different from PATA and SATA in that SCSI devices connect together in a string of devices called a daisy chain

A SCSI host adapter card can support internal and external SCSI devices

Internal & External SCSI Each SCSI device is assigned a SCSI ID (0 - 15) SCSI chains use a terminating resistor Categories of SCSI Connectors Most people set the host adapter to 7 Plugged into last device at both ends of the chain 8-bit (narrow SCSI) Reduces electrical noise or interference on the cable 16-bit (wide SCSI)

External Drive Interfaces Motherboards can provide external SATA (eSATA) ports eSATA drives use a special shielded serial ATA cable and the port is shaped different than internal SATA eSATA supports speeds of 6 Gb/s Almost every computer has USB ports USB 3.0 supports speeds up to 5 Gb/s and cables over 16’ long Many computers have a Firewire port Firewire 800 supports speeds up to 800 Mb/s and cables over 15’ long