Computer Storage Device


Computer Storage Device, Solid State Hard Drive, Mechanical Hard Drive, RAID Array

  • Background
  • Windows Disk Format
  1. Partition Tables
    1. GUID Partitition Table (GPT)
      1. Typical partition table for most disks since allows virtually unlimited disk size (9 Zettabytes = 9 Billion Terabytes)
    2. Master Boot Record (MBR)
      1. Older legacy systems and tools (e.g. Microsoft Recovery Tool still creates MBR) allow a maximum of 2 terabytes
  2. File systems
    1. New Technology File System (NTFS)
      1. Default file system on Windows client and server machines (replaced FAT, FAT32, ExFat)
      2. Is read-only when used on a Mac (use ExFat instead for external discs used for both OS)
    2. Extended File Allocation Table (ExFat)
      1. Older file format allows read/write on both Windows and Mac
      2. Optimized for SSD, SD cards
    3. Resilient File System (ReFS)
      1. Windows server file system option (starting with 2012)
      2. Ultimately Microsoft intends to replace NTFS with ReFS
  3. Utilities
    1. Disk Management utility (or from within Computer Management Utility)
    2. Diskpart (command-line utility, type Diskpart at command line or powershell to start)
      1. List Disk, List Partition, List Volume
    3. Powershell
      1. Get-Disk
  4. References
    1. Warner (2016) Comptia A+, Pluralsight
  • Types
  • Storage Devices
  1. Mechanical Hard Drives (magnetic hard disks)
    1. Aluminum platters spin (7200 rpm on desktop, faster = less latency) under actuator arm with read-write head
    2. Iron oxide on surface can be magnetized and represent individual bits (1=magnetic, 0=unmagnetized)
    3. Each disc has heads (sides), tracks (concentric rings), sectors (pie slice of platter, 512B), clusters (track sections)
      1. Sectors are grouped into clusters
      2. Each cluster is the smallest amount of disk space an file will be written
        1. NTFS will typically have 4 KB clusters (exception: 8-64 KB if drive/volume >16 TB)
        2. ExFat will typically have 128 KB clusters (unless drive <32 GB)
      3. Files are saved to complete clusters (e.g. a 6 kb file would use an 8 kb cluster)
    4. Hard drive enclosures allow USB access to internal drive (e.g. from failed system)
  2. Solid State Devices
    1. Solid State Hard Drives (SSD)
      1. Modern, more expensive, faster drives with non-volatile RAM, gradually replacing mechanical drive
      2. Flash drives can fail suddenly (contrast with mechanical drives which often gradually fail)
    2. Flash Memory Cards (compact flash, SD, micro SD)
      1. Number on card represents flash memory speed rating (higher numbers, e.g. 10, are faster)
    3. USB Keys (thumb drive, USB memory stick)
      1. Available with encryption and password protection (even with keypad on USB key)
  3. Optical Drives (CD, DVD, Blue Ray)
    1. At least with computer use, replaced by more durable, faster and higher capacity devices
  4. Tape Drives and Magnetic Tape Data Storage
    1. Large capacity tape (e.g. 500 GB) still used for longterm, reliable data backup (often off-site)
  • Typres
  • Interfaces (primarily Mechanical Hard Drives)
  1. Parallel ATA (PATA) or Enhanced Integrated Drive Electronics (EIDE, IDE)
    1. Older, slower, 40 pin ribbon cable connected drives, configured with jumper connectors
  2. Serial ATA (SATA or eSATA)
    1. Modern drive interface for desktop and server machines (set-up without jumpers; set in BIOS)
    2. SATA speeds increase from SATA 1 (1.5 GBit/s), SATA 2 (3 GBit/s) to SATA 3 (6 GBit/s)
  3. Small Computer System Interface (SCSI)
    1. Older, parallel protocol, which allowed daisy-chaining of devices; replaced by SAS (serial SCSI)
  4. Serial Attached SCSI (SAS)
    1. Modern serial SCSI interface for multiple drives daisy-chained used in high-end machines and servers
    2. Internal and external drives are attached to a host bus adapter
  • Types
  • Redundant Array of Independent Disks (RAID) Types
  1. Precautions
    1. RAID is best coordinated by a dedicated expansion card (hardware instead of software) for best performance
    2. RAID is not a replacement for system backup
  2. RAID 0 (Striping optimizes for speed)
    1. Data is striped across 2 disks, allowing for rapid data read/write (however, all data is lost when 1 drive fails)
  3. RAID 1 (Mirroring optimizes for redundancy)
    1. Identical data is written to each of 2 mirrored disks (at expense of losing 50% of available storage)
  4. RAID 5 (Disk Striping AND Parity/redundancy)
    1. Data is striped across at least 3-4 disks, with Parity data written to another drive
  5. RAID 01 or RAID 0+1 (Combines RAID 0 and RAID 1)
    1. One pair of drives is striped (RAID 0) and then the drive pair is mirrored to another drive pair (RAID 1)
  6. RAID 10 or RAID 1+0 (Combines RAID 1 and RAID 0)
    1. One drive is striped with another and each drive is mirrored to another set of drives
  7. Resources
  • Differential Diagnosis
  • Storage Problems
  1. Precautions
    1. All hard drives (mechanical and SSD fail) unexpectedly
    2. Frequent backups are key
    3. Consider RAID Array
  2. Mechanical Hard Drive Head Crash
    1. Read/Write Head may be disrupted from disk platter with system jarring or fall
  3. Read-Write Failure
    1. Data-cable defect (try a different SATA cable)
    2. Hard disk defect (clone immediately to retain as much data as possible)
  4. Slow disk performance
    1. Limited free space on operating system drive (e.g. C:\)
    2. Fragmentation (Defragment Mechanical Hard Drives, but NOT SSD)
  5. Loud clicking or clunking noise
    1. Expect a quiet chirping from Mechanical Hard Drives in general
    2. Drive failure (clone immediately to retain as much data as possible)
  6. Drive not recognized
    1. Loose or missing SATA cables
  • Management
  • Storage Devices Software Tools
  1. Defragmentation software (e.g. windows)
    1. Only defragment Mechanical Hard Drives
    2. Do NOT defragment SSD or Solid State Drives
      1. SSD defragmentation shortens life of SSD drive
      2. Unlike, mechanical drives, SSD Defragmentation does not offer significant performance benefit
      3. TRIM command can be used with SSD to mark open areas of writeable memory
  2. Self Monitoring, Analysis and Reporting Technology (SMART)
    1. Various software packages (e.g. Crystal Disk Info) predicts drive failure before it occurs (based on disk metadata)
  3. File Recovery Software
    1. Acronis Backup
    2. Windows File History (must be enabled)
    3. Apple Time Machine
  4. Windows command line utilities (run in Powershell)
    1. Background
      1. Command line tools are largely replaced by powershell (and graphical utilities)
      2. These command line tools are still used to create scripts to perform task automatically (bat files)
    2. Chkdsk
      1. Chkdsk /?
        1. Provides help
      2. Chkdsc c:
        1. Checks the C drive (and should return "..found no problems, no further action required")
    3. Format
      1. Formats a hard drive (careful - confirm the correct hard drive letter!)
    4. DiskPart
      1. Prompt becomes "DISKPART"
      2. "Help" displays help information
      3. List disk wil display disk information (similar to powershell "get disk")
      4. Allows for partitioning and defragmentation from the command line
    5. BootRec
      1. Utility that repairs critical disk structures
  5. Windows GUI Utilities
    1. Optimize Drives (and defragment)
      1. Allows for automation of Mechanical Hard Drive defragmentation on a scheduled basis
      2. SSD Drives will be defaulted to TRIM command (not defragmentation)
    2. Windows Explorer Disk Properties
      1. Tools Tab has links to GUI versions of "Check Disk" and "Optimize"
    3. Computer Management - Disk Management Tab (or Disk Management Utility)
      1. Allows visualization of disks and tools for formatting/partitioning
  6. Windows Powershell
    1. Get-Command -Module Storage | Select-Object -Property Name
    2. Get-Disk
  • References
  1. Warner (2015) CompTIA A+, Pluralsight