Storage Devices and Their Configurations

Location Services

  • Location services allow mobile devices to understand their geographical position on Earth.
  • There are three basic types of location services:
    • GPS (Global Positioning System)
    • Wi-Fi positioning
    • Cell tower triangulation

Storage Devices

  • Overview of storage devices covered in this section:
    • Hard Disk Drives (HDD)
    • Solid State Drives (SSD)
    • RAIDs (Redundant Array of Independent Disks)
    • Removable storage devices
    • Optical drives

Persistent Storage

  • Persistent storage is required to retain data when a computer is powered off.
  • Examples of persistent storage include HDDs and SSDs.
  • Volatile storage (CPU cache and RAM) loses its data when powered off.

Comparing Storage Devices (Objective 3.4)

  • The focus will be on comparing and contrasting various storage devices.

Hard Disk Drives (HDD)

  • Commonly referred to as hard disks or hard drives.
  • Long-standing technology popular due to:
    • Relatively low cost
    • High storage capacity

Solid State Drives (SSD)

  • Referred to as solid state devices.
  • Advantages:
    • Faster than HDDs
    • No moving parts, leading to less risk of physical damage.
  • Disadvantages:
    • 2-3 times more expensive than HDDs for the same capacity.

RAIDs

  • RAID configurations combine multiple physical drives into a single logical unit.
  • Advantages include improved speed and redundancy.
  • Definitions of RAID:
    • RAID: Redundant Array of Independent Disks (or Inexpensive Disks).

Removable Storage Devices

  • Examples include flash drives and memory cards.
  • Types of removable storage:
    • USB drives
    • External hard drives
    • Optical storage media (CDs, DVDs, Blu-ray)

Mass Storage Devices

  • Mass storage devices categorized as:
    • Internal: Hard disk drives, SSDs, optical drives, tape drives, floppy drives.
    • External: Connect outside the computer case.
  • Sizes of devices encountered:
    • 2.5 inch (typically internal HDDs/SSDs)
    • 3.5 inch (usually internal HDDs)
    • 5.25 inch (for optical drives)
  • Drive bay adapters can allow smaller drives to fit into larger bays.

Hard Disk Drive Mechanics

  • HDDs store data on magnetic platters.
  • Access managed via a read/write head and actuator mechanism.
  • Key terms:
    • Tracks: concentric circles on platters
    • Sectors: segments of tracks, typically 512 bytes each.
    • Data access speed depends on RPMs (Revolutions Per Minute). Common RPMs:
    • 5,400 RPMs: Budget or low-end workstations.
    • 7,200 RPMs: Standard for many computers.
    • 10,000 RPMs: High performance, for servers and gaming PCs.
    • 15,000 RPMs: High-end servers, now typically less common due to SSD alternatives.

Buffer Size in HDDs

  • The buffer size impacts performance; ranges from 8MB to 256MB.
  • Larger buffers improve overall performance.

Connecting Hard Drives

  • Connection types depend on the hard drive type and motherboard.
  • Modern systems mostly use:
    • SATA: 1.5, 3, or 6 Gbps speeds (with relevant throughput rates)
  • Legacy systems may use IDE/PATA:
    • 40-wire or 80-wire cables for data and power.
  • SCSI interfaces may be present:
    • Narrow SCSI supports 7 devices.
    • Wide SCSI supports up to 15 devices.
  • SAS (Serial Attached SCSI) offers high speed and compatibility with SATA devices.

Factors for Choosing Drives

  • Critical factors to consider when selecting HDDs vs SSDs:
    • Cost (HDDs generally cheaper)
    • Performance (SSDs outpace HDDs)
    • Capacity (HDDs provide larger storage)

Solid State Drives (SSD)

  • Utilize flash memory technology for non-mechanical, high-speed storage.
  • Advantages:
    • Immediately accessible as there are no moving components.
    • More durable than HDDs when dropped.
  • Formats include:
    • 2.5 inch, 1.8 inch, and M.2.
  • Connection types:
    • Older SSDs use SATA connectors.
    • NVMe significantly improves speeds compared to SATA.
    • PCIe slots can also be used for SSD connections.
  • Typical usage: OS/application storage on SSD with additional HDD for bulk storage.

Hybrid Drives

  • Combine HDD with SSD technology, storing frequently accessed files on SSD.
  • Less popular due to emergence of dedicated SSD + HDD combinations.

RAIDs: Overview

  • RAID types pertinent to study:
    • RAID 0: Striping (no redundancy, increased speed).
    • RAID 1: Mirroring (full redundancy, halved capacity).
    • RAID 5: Parity-based redundancy (minimum 3 disks).
    • RAID 6: Double parity (minimum 4 disks).
    • RAID 10: Combination of RAID 1 and 0 (speed and redundancy).
RAID 0
  • Increased speed but no fault tolerance. Split data across drives.
RAID 1
  • Provides redundancy via mirroring but halves storage capacity.
RAID 5
  • Offers redundancy through parity with a capacity loss of one disk.
RAID 6
  • Similar to RAID 5 but allows for two disks to fail.
RAID 10
  • Combines mirroring and striping, requiring minimum four drives.

Categories of RAID Systems

  • Failure resistant (e.g., RAID 1, RAID 5).
  • Fault tolerant (e.g., RAID 1, RAID 5, RAID 6).
  • Disaster tolerant (e.g., RAID 10).

Removable Storage

  • Definition: Storage devices that can be transferred from one machine to another without physical modifications.
  • Hot-swappable interfaces: USB, Thunderbolt, eSATA.
Hot-swappable Drives
  • Must enable AHCI for SATA to function as hot-swappable.
External Hard Drive Enclosures
  • Internal drives inserted into protective enclosures for external use.
Flash Drives
  • Portable storage devices, largely USB-based, utilizing flash memory.
Memory Cards
  • Formats include SD, Mini SD, Micro SD. Speed and capacity vary.
Tape Drives
  • Historically used for backups, still relevant in certain corporate environments.
  • Standard tapes hold ~140GB; LTO Ultrium tapes can hold up to 3TB.
Floppy Drives
  • Legacy devices, commonly holding 1.44MB data; still used in some specialized applications.

Optical Drives

  • Types: CDs, DVDs, Blu-ray discs.
  • Storage capacity:
    • CD: 650MB to 700MB.
    • DVD: 4.7GB (single layer) to 8.4GB (dual layer).
    • BluRay: 25GB (single layer) to 50GB (dual layer).
  • Three categories of optical media:
    • Read-Only (ROM)
    • Write-Once (R)
    • Rewritable (RW)
  • Important speeds: CD drives operate at 52x, DVD drives at ~24x, Blu-ray drives at 8x.
Installation of Optical Drives
  • Requires a 5.25 inch internal bay and standard SATA connection for data and power.