CompTIA A+ Cert Exam Guide Ch. 11 - Hard Drive Technologies Flashcards
What does a traditional hard drive consist of?
Individual disks, or platters, with read/write heads on actuator arms controlled by a servo motor-all contained within an airtight case.
What is a flux?
A small magnetic field on the hard drive disk used for the storage of data. The polarity of the field can be switched between north and south polarity.
What is flux reversal?
The process of shifting the magnetic field of a flux from north to south or vice versa.
What is a run?
A group of fluxes read by a HDD
What is Run Limited Length?
RLL; An encoding system of any combination of ones and zeros stored in a preset combination of about 15 runs on a HDD
What is Partial Response Maximum Likelihood encoding?
PRML; Powerful, intelligent circuitry used to analyze flux reversal to make a “best guess” as to what type of flux reversal it has just read. The maximum run length is up to 16-20 fluxes vs. the 7 of RLL.
What is perpendicular recording?
The vertical storage of fluxes on a HDD vs. storing them longitudinally. This allows for a much more densely packed HDD.
What are actuator arms/head actuators?
The piece(s) that are attached to the read/write heads that allow them to move across the platters
What are the two types of motors used to move the actuator arms?
- Stepper motor
* Voice coil/linear motor
How does the stepper motor function?
It moved the arms in fixed increments or steps across the platters.
What were the limitations of the stepper motor?
- It required minimal slippage to maintain accuracy. Over time, the position of the arms could change with wear, causing data transfer errors
- Heat deformation created problems with stepper motors
- The stepper motor needed to be parked when off. If the read/write heads were not parked when handling the drive, they could cause damage to the platters.
How does the linear motor function?
Voice Coil Motor; Uses a permanent magnet surrounding a coil on the actuator arm. When an electrical current passes, the coil generates a magnetic field that moves the actuator arm. The direction of the movement depends on the polarity of the electrical current.
What are the advantages of the linear motor over the stepper motor?
- Because the coil and the actuator arm never touch, there is no degradation of positional accuracy
- The linear motor automatically parks the read/write heads
What is the geometry of a disk?
The magnetized pattern in which a hard drive disk stores data. Ever model (brand?) of HDD uses a different pattern.
The geometry is describes with a set of numbers representing 3 things: heads, cylinders, and sectors per track
What are heads?
The read/write heads used to store data. Every platter requires two.
What is a cylinder?
A group of tracks with the same diameter
What are sectors per track?
The number of sectors per track on a HDD
What is a sector?
A specific piece of track on a HDD platter.
What is the write precompensation cylinder?
Older drives had trouble reconciling the smaller sectors towards the inside of the platter. To compensate for this, the drive would spread data on the inside of the platter a bit farther apart. The drive would need to know where this began.
What is a landing zone?
An unused cylinder used as a “parking space” for the read/write heads. When not in use, the read/write heads were parked in the landing zone so as to prevent damage to the platters when the disk was moved.
How is the speed of a drive measured?
The speed of a drive is measured in revolutions per minute (RPM). Common drive speeds are 5400, 7200, 10,000, and 15,000 RPM. Faster drives means better performance, but also the possibility of overheating your computer.
What is a Solid State Drive?
SSD; A hard drive that uses a series of memory chips rather than platters, etc. to store data. As a result, SSDs have no moving parts. Instead, they use current flow and negative/positive electron charges to store and retrieve data.
Some facts:
• Form factors - 1.8-inch, 2.5-inch, and 3.5-inch
• Can be PATA, SATA, eSATA, SCSI, or USB
• SSDs that use SDRAM will lose data when powered off. SSDs that use nonvolatile memory, such as NAND, retain data when powered off
• Less expensive SSDs utility multi-level cell (MLC) memory technology whereas more expensive SSDs use single-level cell (SLC) technology
ATA
Advanced Technology Attachment
IDE
Integrated Drive Electronics; Any hdd with a built-in controller is considered an IDE hdd.
SCSI
Small Computer System Interface
PATA
Parallel ATA; Data is sent in parallel on a 40- or 80-wire data cable
SATA
Serial ATA; data is sent in serial on a single wire
What are the two types of ATA drives?
- Parallel ATA (PATA)
* Serial ATA (SATA)
What is an external enclosure?
The name used to describe the casing of an external hard drive
How did the early ATA drives connect to the motherboard?
A 40-pin cable with a colored stripe down one side that denotes pin 1 on the drive and controller.
What does the drive controller on the motherboard do?
Nothing. It acts as an intermediary between the drive and the motherboard, but the BIOS speaks with the controller on the drive itself.
How many drives could you connect to a single IDE connector on a single ribbon cable?
Two drives, a master and a slave drive.
How do you distinguish between a master and a slave drive?
The jumpers on the back of the drive indicate whether the drive is a master or slave
What things must you define to make a hard drive standard?
The method and the speed at which the data is going to move
PIO
Programmed I/O; the CPU talks directly with the HDD via the BIOS to send and receive data Speeds: • PIO mode 0: 3.3 MBps • PIO mode 1: 5.2 MBps • PIO mode 2: 8.3 MBps • PIO mode 3: 11.1 MBps (ATA-2) • PIO mode 4: 16.6 MBps (ATA-2)
DMA
Direct Memory Access; enabled the HDDs to talk to RAM directly using old-style DMA commands. Speeds: • Single-word DMA mode 0: 2.1 MBps • Single-word DMA mode 1: 4.2 MBps • Singe-word DMA mode 2: 8.3 MBps • Multi-word DMA mode 0: 4.2 MBps • Multi-word DMA mode 1: 13.3 MBps • Multi-word DMA mode 2: 16.6 MBps
EIDE
Enhanced IDE; a marketing term referring to the second manifestation of the ATA form factor
What advancements did the ATA-2 form factor provide?
- Higher capacities
- Support for non-hard drive storage devices
- Support for two or more ATA devices for a maximum of 4
- Improved throughput
What was the largest supported hard drive disk under the original AT standard?
504 MB
• 528 million bytes
• 1024 cylinders, 16 heads, and 63 sectors/track
LBA
Logical Block Addressing
What two drive geometries did the ATA specification have?
- Physical Geometry - the actual physical layout of the CHS inside the drive
- Logical Geometry - the layout the drive communicated to CMOS
What is sector translation?
The translation of the physical drive layout to the logical drive layout that the drive communicates to the CMOS
What is ATAPI?
Advanced Technology Attachment Packet Interface; Allows non-hard drive devices such as CD-ROM drives and tape drives to connect to the PC via the ATA controllers. Non-hard drives require the OS to load software drivers for BIOS support.
What feature did ATA-3 add?
S.M.A.R.T.; Self-monitoring, Analysis, and Reporting Technology
What function doe S.M.A.R.T. serve?
It helps predict when a hard drive is going to fail by monitoring the hard drive’s mechanical components
Ultra DMA modes as defined by ATA-4
- Ultra DMA mode 0: 16.7 MBps
- Ultra DMA mode 1: 25 MBps
- Ultra DMA mode 2: 33.3 MBps
What is INT13?
Interrupt 13 extensions; A new set of BIOS commands that ignored the Cylinder - Head - Sector (CHS) values and instead fed the LBA a stream of addressable sectors.
Ultra DMA modes added by ATA-5
- Ultra DMA mode 3: 44.4 MBps
* Ultra DMA mode 4: 66.6 MBps
How did ATA-5 change the cable to allow for the higher speeds of Ultra DMA modes 3 and 4?
It added an 80 wire cable that consists of 40 wires and pins with 40 ground wires. It also set specific connectors for each device:
Blue - HDD controller on the motherboard
Grey - Slave drive
Black - Master drive
What is ATA/33?
Another name for ATA-4 Ultra DMA mode 2: 33.3 MBps
What is ATA/66?
Another name for ATA-4 Ultra DMA mode 4: 66.6 MBps
What changes did the ATA-6 standard bring?
- Big Drive, otherwise known as ATA/ATAPI-6 or ATA-6
- A drive size limit of 144 petabytes
- 48-bit LBA
- Enhanced block mode, enabling drives to transfer up to 65,536 sectors in one chuck, vs. the previous limit of 256 sectors
- Ultra DMA mode 5: 100 MBps
What changes did ATA-7 bring?
- Serial ATA
* Ultra DMA mode 6: 133 MBps
What were the disadvantages of parallel ATA?
- The ribbon cabled impede airflow and are difficult to install
- The cables are limited to 18 inches in length
- PATA drives are not hot swappable
- The technology has reached its limit where throughput is concerned
HBA
Host Bus Adapter
What advantages does SATA have over PATA?
- Because data is transferred serially, the cable only requires 7 wires, making it significantly thinner.
- The maximum length of the cable is 40” rather than 18”
- SATA does not use the master/slave setup and has eliminated the maximum number of drives
What three varieties do SATA drives come in?
- SATA 1.0: 1.5 Gbps - throughput of 150 MBps
- SATA 2.0: 3 Gbps - throughput of 300 MBps
- SATA 3.0: 6 Gbps - throughput of 600 MBps
Can a PATA drive be plugged into a SATA controller?
Yes. You can use a SATA bridge to use a PATA drive. The bridge requires its own power source.
AHCI
Advanced Host Controller Interface; ACHI enables the advanced features of SATA drives, such as the hot swappable feature. It is implemented at the CMOS level. It needs to be enabled before installing the OS.
How do you add a HDD on a computer that isn’t running AHCI?
- Windows XP/Vista: Control Panel > Add New Hardware
* Windows 7: Start Menu Search > hdwwiz.exe
NCQ
Native Command Queuing; a disk optimization feature for SATA drives that enables faster read/write speeds
