1.05 Select and install storage devices

Introduction 

Computers help us create and manage data. But where is the data kept? Storage devices are like bookshelves in a library—they hold and organize information. Just as you find a book on a shelf to read, you access files on a storage device to use them.

But why choose one storage device over another? And how do these devices store data? This lesson will explore the different types of storage devices and their best uses.

What’s a Mass Storage Device? 

Mass storage devices are non-volatile storage devices, which means that they keep data even when the computer is turned off. 

  • Types of Technology: Mass storage devices use magnetic, optical, or solid-state technology to store data. 

  • Fixed Disks: When a mass storage device is installed inside a computer, these devices are called fixed disks. They come in standard sizes like 5.25, 3.5, and 2.5 inches. 

  • Drive Bays and Caddies: Computers have drive bays to fit these sizes, and caddies help secure the drives or adapt different-sized drives to fit. You screw the drive into the caddy, then screw the caddy into the drive bay. 

  • Removable and External Devices: Some mass storage devices are removable or external, like USB drives, for easy data transfer or backup. 

  • Factors to Consider: Important factors in choosing a storage device include reliability, performance, and intended use.  

    • Reliability: How likely is the device to fail? How likely is data corruption? 

    • Performance: Is it able to read or write data fast enough? What ability is most important for its intended use? 

    • Intended Use: Is speed or the amount of storage available most important? What will give me what I need while still staying within budget? 

  • Common Brands: Popular brands for mass storage devices include Seagate, Western Digital, Hitachi, Fujitsu, Toshiba, and Samsung. 

Solid State Drives 

Solid-state drives (SSDs) use flash memory technology for persistent storage, offering better performance and reliability than traditional hard disk drives (HDDs).

  • Performance and Reliability: SSDs generally perform better than HDDs, especially in read speeds and resistance to mechanical shock, though they can be slower with very large files. They are less prone to failure due to a lack of mechanical parts. 

  • Flash Memory Types: SSDs use NAND flash memory, which can degrade over many write operations. To counter this, wear leveling techniques are used to evenly distribute data writing across all memory cells. Single-level cell (SLC) flash is more reliable but more expensive than multi-level cell (MLC) types. 

  • Installation Configurations: In desktops, SSDs can serve as the main internal drive or as a boot drive paired with an HDD for additional storage. SSDs can connect via different interfaces: a 2.5-inch SATA, mSATA, or PCI Express (PCIe). SATA interfaces can limit performance to 600 MBps, while PCIe SSDs, using NVMe, can reach speeds up to 6.7 GB/s. 

  • M.2 Form Factor: M.2 is a small form factor for SSDs, often used in laptops and modern motherboards. M.2 SSDs can use either SATA/AHCI or NVMe interfaces, affecting performance. They come in various sizes, like M.2 2280, indicating width and length, and can have different key types (B, M, or B/M keyed) depending on the supported interface. 

  • Handling Precautions: SSDs are sensitive to electrostatic discharge (ESD), so anti-ESD measures should be taken when handling and installing them. 

Size examples of M.2 SSDs. The first two digits of the size number are the width and the remaining digits are the length in millimeters; a 2242-sized M.2 SSD is 22mm x42mm.

Analogy: Think of an SSD like a race car on a smooth, paved track. It can accelerate quickly and navigate turns with ease (fast read speeds and low latency) compared to an HDD, which is like a heavy truck on a bumpy dirt road—it moves slower and can’t handle rough terrain as well (lower performance and more prone to mechanical failures). However, just like race cars aren't great for hauling large amounts of cargo, SSDs can slow down when handling extremely large files. 

Hard Disk Drives 

Hard disk drives (HDDs) store data on spinning platters using magnetic technology, with performance largely dependent on the speed of these platters and other mechanical factors. 

  • Data Storage Technology: HDDs store data on metal or glass platters coated with a magnetic material. Data is accessed by read/write heads that move across the platters, which are divided into circular tracks and sectors. 

Analogy: Think of an HDD like a vinyl record player. The platters inside the HDD are like the vinyl discs, each coated with a magnetic "groove" where data is stored. The read/write heads are like the needle of the record player, moving back and forth across the platters to "play" (read) or "record" (write) the information stored in these magnetic tracks and sectors.

  • Components and Mechanics: The platters spin on a spindle at high speeds, with each side accessed by its own read/write head, moved by an actuator mechanism. The speed of the platters is measured in revolutions per minute (RPM), with common speeds being 15,000, 10,000, 7,200, and 5,400 RPM. 

  • Performance Factors: Performance is influenced by RPM, seek time (the time it takes for the read/write head to locate a track), and rotational latency (the delay caused by the sector location on the spinning platters). High-performance drives have lower access times, typically below 3 milliseconds. 

  • Transfer Rates: The internal transfer rate measures how quickly data is read or written on the disk. A 15,000 RPM drive can reach up to 180 MBps, while a 7,200 RPM drive is around 110 MBps. 

  • Interfaces and Form Factors: Most HDDs use a SATA interface, though some older models use EIDE/PATA or SCSI. HDDs come in two main sizes: 3.5-inch for desktops and 2.5-inch for laptops and external drives, with 2.5-inch drives also available in different heights like 15 mm, 9.5 mm, 7 mm, and 5 mm. 

What are Removeable Storage Drives? 

Removable storage refers to devices or media that can be easily moved between computers without needing to open the computer case.

  • Drive Enclosures: Enclosures for HDDs and SSDs provide protection and interfaces like USB, Thunderbolt, or eSATA. Some can connect directly to a network (NAS) and support multiple drives in a RAID configuration. 

  • Flash Drives and Memory Cards: Flash memory can be used in USB flash drives or memory cards, commonly used in cameras, smartphones, and tablets. These devices are portable and connect via USB ports or card readers. 

  • Memory Card Readers: PCs can have built-in or external card readers to support various memory card types, connecting to the computer via USB ports or expansion cards. 

  • Types and Capacities: Memory cards, such as SD, SDHC, and SDXC, come in different sizes and capacities, ranging from 2 GB to 2 TB, with speed ratings from 25 MBps up to 624 MBps depending on the card type and version. 

  • Standard SD (SDSC) Capacity: 128 MB to 2 GB

  • SDHC (Secure Digital High Capacity) Capacity: 4 GB to 32 GB

  • SDXC (Secure Digital Extended Capacity) Capacity: 64 GB to 2 TB

  • SDUC (Secure Digital Ultra Capacity) Capacity: 2 TB to 128 TB

  • Adapters and Compatibility: Smaller cards like microSD can be used with standard-sized readers using adapters (caddies), making them versatile for different devices.

What’s an Optical Drive? 

Optical drives use lasers to read and write data on discs like CDs, DVDs, and Blu-ray Discs, which are commonly used for storing music, videos, and PC data. 

  • Types of Discs and Formats: CDs, DVDs, and Blu-rays come in three main types: recordable (write once), multisession recordable (write multiple times without erasing), and rewritable (write and erase multiple times). 

  • Capacities and Transfer Rates: CDs hold up to 700 MB with a base transfer rate of 150 KBps; DVDs range from 4.7 GB to 17 GB with a base transfer rate of 1.32 MBps; Blu-rays hold 25 GB per layer with speeds up to 72 MBps. 

  • Installation and Connections: Internal optical drives fit into a 5.25-inch drive bay and connect via SATA, while external drives connect through USB, eSATA, or Thunderbolt and usually need an external power supply. 

  • Eject Mechanisms: Drives have a manual eject mechanism (activated with a paper clip) for use when the regular button or power is unavailable. 

  • Speed Ratings: Drives are rated by their record/rewrite/read speeds (e.g., 24x/16x/52x), with modern drives supporting multiple formats, but older drives may not support Blu-ray. 

  • Copy Protection: DVDs and Blu-rays may have DRM and region-coding to prevent copying and restrict playback to specific geographic regions. On PCs, the region can only be changed a limited number of times. 

Storage Device Configurations 

A Redundant Array of Independent Disks (RAID) is a system that combines multiple HDDs or SSDs to provide data redundancy and fault tolerance, preventing data loss in case of a drive failure. 

  • Purpose: RAID is used to prevent data loss if a system's boot or data drive fails by creating a redundant storage setup that appears as a single volume to the operating system. 

  • RAID Levels: Different RAID levels (0 to 6, plus nested levels like RAID 10) provide various types of fault tolerance and performance improvements, with each level offering different configurations and redundancies. 

  • Implementation: RAID can be set up using software (built into the operating system) or hardware (using a dedicated controller card). Hardware RAID is often more reliable and supports more RAID levels. 

  • Motherboard RAID: Some motherboards include built-in RAID capabilities as part of their chipset, allowing for easy RAID configuration without additional hardware. 

  • Hardware RAID Advantages: Hardware RAID controllers can support hot swapping, meaning a failed drive can be replaced without shutting down the system, minimizing downtime and data loss risk. 

Redundant Array of Independent Disks (RAID) 

When choosing between RAID levels, it's important to consider the level of fault tolerance, performance needs, required capacity, and cost. Here’s a summary of RAID 0 and RAID 1: 

Disk Requirements: All disks in a RAID array should ideally be the same size and type for optimal performance. If disks differ in size, the smallest disk dictates the maximum usable capacity across the array. 

RAID 0 (Striping without Parity) 

  • How It Works: RAID 0 splits data into blocks and distributes these blocks across multiple disks, allowing for faster read and write performance since multiple disks work in parallel. 

  • Requirements: Requires at least two disks. The total storage capacity is the combined size of the smallest disks in the array. 

  • Advantages: Improved performance due to parallel processing of data requests. 

  • Disadvantages: No redundancy; if one disk fails, all data in the array is lost, making RAID 0 suitable only for non-critical tasks where data loss is acceptable.

Analogy: Imagine a factory with several conveyor belts (disks) lined up next to each other. Each conveyor belt handles a different part of the assembly process (data). Because multiple conveyor belts work simultaneously, the overall production (data processing) is much faster. However, if one conveyor belt breaks down, the entire production line stops because each belt is dependent on the others to complete the product.

RAID 1 (Mirroring) 

  • How It Works: RAID 1 duplicates all data on two disks, providing a mirror copy. If one disk fails, the other can continue to operate with minimal impact on system availability. 

  • Requirements: Requires exactly two disks. Storage capacity is equal to one of the disks, as all data is duplicated. 

  • Advantages: Provides fault tolerance by maintaining a complete copy of data on each disk. Minimal performance impact during normal operations, with improved read performance since data can be read from either disk. 

  • Disadvantages: Higher cost per gigabyte since only 50% of total disk space is usable. If a disk fails, rebuilding (copying data to a new disk) is quicker compared to other RAID levels, but performance is still reduced during this process.

RAID 5 and RAID 10 offer a balance of performance, disk utilization, and fault tolerance, making them advantageous over simpler RAID levels like RAID 1. 

RAID 5 (Striping with Distributed Parity) 

  • How It Works: RAID 5 stripes data across multiple disks while also distributing parity (error correction) information across all disks. This allows for data recovery if a single disk fails. 

  • Requirements: Requires a minimum of three disks. The usable capacity is the total capacity of all disks minus one (for parity). 

  • Advantages: Good read performance and efficient use of disk space compared to RAID 1. If a single disk fails, data can still be accessed and reconstructed. 

  • Disadvantages: Write performance is slower due to the need for parity calculations. If more than one disk fails, all data is lost. Read performance is also degraded when a disk has failed, as data must be reconstructed using parity. 

Analogy: Think of a group of people working together to complete a large jigsaw puzzle (data). They occasionally take pictures (parity) of the puzzle as they progress. If someone accidentally knocks over the puzzle and loses a few pieces (disk failure), they can look at the latest picture to figure out where the missing pieces should go and recreate the lost part of the puzzle. This way, they don't have to start over completely, but it takes a bit longer to reconstruct the lost section. 

RAID 10 (Stripe of Mirrors) 

  • How It Works: RAID 10 combines RAID 1 (mirroring) and RAID 0 (striping), creating a striped set of mirrored disks. This means data is mirrored across pairs of disks and then striped across those pairs. 

  • Requirements: Requires a minimum of four disks and must have an even number of disks. Each pair of disks is mirrored, and the pairs are striped together. 

  • Advantages: Provides excellent fault tolerance and performance. Even if one disk in each mirrored pair fails, the array remains functional. 

  • Disadvantages: High cost per gigabyte due to 50% disk space overhead, as half of the total storage is used for mirroring. 

Summary 

Well done, that was a lot of information. By now, you should have a good understanding of what storage devices are, the various types available, how they differ from one another, and the best ways to use them both on their own and in different setups.

Be sure to use the study aids to help you memorize key concepts, such as how different RAID configurations work and their functionalities.