Hard Drive Technologies

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					Hard Drive Technologies

             Joe Cicero
    Northeast Wisconsin Technical College
This Presentation Will Cover…
   Types of Hard Drives
       SATA, ATA, SCSI, etc
   Hard Drive Parts
       Platter/s, Read/Write Head/s, Actuator Arm/s,
        Actuator, Spindle, etc.
   How A Hard Drive Works
       Modifying Magnetic Media
   Hard Drive Math
       Why 1000 = 1024
                  Continued…
   Hard Drive Controllers
       IDE, EIDE, SCSI, SATA, RAID, etc
   Configuring Hard Drives
       Jumpers, Master, Slave, Cable Select, IDE /
        EIDE Cable capabilities, etc.
   Partitioning A Hard Drive
       Primary, Extended, Logical Drives
   Format of Hard Drive
       FAT, NTFS, EXT3, etc
                   Continued…
   Hard Drive Maintenance
       Chkdsk, cleanmgr, defrag, limitations, etc.
              Types of Hard Drives

   Hard drives come in many different types.
    Some of these are:
       ATA
         ATA : Also known as IDE (Integrated Drive
         Electronics) supports one or two hard drives per
         cable, a 16-bit interface and PIO (Programmed
         Input/Output).
ATA Hard Drive
Types of Hard Drives Continued:
   SATA
     SATA    or S-ATA, an evolution of the ATA physical
      storage interface. Serial ATA is a serial link -- a
      single cable with a minimum of four wires creates a
      point-to-point connection between devices.
      Transfer rates for Serial ATA begin at 150 MBps
      and SATA II 300MBps.
     One of the main design advantages of Serial ATA
      is that the thinner serial cables facilitate more
      efficient airflow inside a form factor and also allow
      for smaller chassis designs.
SATA Hard Drive
    Types of Hard Drives Continued:
   SCSI
       This acronym is pronounced "scuzzy" and stands for Small
        Computer Systems Interface. IDE and SATA are much more
        common and less expensive.
       The biggest difference between SCSI, ATA and SATA is that
        while SCSI has a processor integrated into the controller, ATA
        and SATA make greater use of the system processor to serve
        that function.
       SCSI is more expensive and also more flexible and generally the
        drive spins faster – but it should be noted that spinning faster
        doesn’t necessarily make it work faster with the OS.
       With a single SCSI card you can have 15 or more devices
        whereas typically you are only allowed to have 4 devices with an
        ATA/IDE or SATA system.
SCSI Hard Drive
Hard Drive Parts




              A - Platter/s
              B - Read/Write Head/s
              C - Actuator Arm/s
              D - Actuator
              E - Spindle
       How A Hard Drive Works
   The banks of polarized molecules in the disk's
    coating are themselves tiny magnets that create
    a magnetic field through which the read/write
    head passes. The movement of the head
    through the magnetic field generates an
    electrical current that travels in one direction or
    the other through the wires leading from the
    head. The direction the current flows depends
    on the polarities pf the bands. By sensing the
    directions in which the current is moving, the
    computer can tell if the read / write head is
    passing over a 1 or a 0.
How A Hard Drive Works
                   Hard Drive Math
   kilo is 1,000 in the decimal system.

   Hence, one kilometer is a 1,000 meters and one kilogram is 1,000
    grams because we are using the decimal system.

   However, in the binary system, a kilo is 1,024.

   As you can see the kilo in the binary system (1,024) is close in value
    to the kilo in the decimal system (1,000) and many people use 1
    kilobyte as a synonym of 1,000 bytes.

   Therefore, a file of 6 KB contains 6,144 bytes (6 x 1024 bytes) not
    6000 bytes. A 2.2 Gig hard drive partition would have
    2,252,800,000 bytes or would be 2.2528 GB.
             Hard Drive Controllers
   IDE
       Integrated Device Electronics. A hard drive interface system developed
        by a group of manufacturers whereby the controller system was
        integrated into the drive; all of the components were within the hard
        drive unit removing the need to have a separate controller.
       It should be NOTED that most older 40 wire IDE cables DO NOT
        support Cable Select!
   EIDE
       A design that improves on the Drive limitations of the IDE design. EIDE
        designs can use up to four devices (split into two pairs). For each pair of
        devices, one of the devices is the master; the drive electronics on the
        master control both the master drive and (if applicable) the secondary
        slave unit attached.
       It should be NOTED that the Master Drive should be plugged into the
        end of the cable if you want it to be a master device and are setting it to
        Cable Select!
           Hard Drive Controllers
   SCSI
       Small Computer Systems Interface, a high-speed
        communications protocol that allows computers,
        samplers, and disk drives to communicate with one
        another. Pronounced "scuzzy.“
       It should be noted that when using SCSI interfaces
        you can have up to 7 (or even 15) devices.
   SATA
       Serial ATA is an evolutionary replacement for the
        Parallel ATA physical storage interface.
             Hard Drive Controllers
    RAID (Redundant Array of Independent Disks). A collection of disk drives
    that offers increased performance and fault tolerance. There are a number
    of different RAID levels. The three most commonly used are 0, 1, and 5:

         * Level 0: striping without parity (spreading out blocks of each file
    across multiple disks).
         * Level 1: disk mirroring or duplexing.
         * Level 2: bit-level striping with parity
         * Level 3: byte-level striping with dedicated parity. Same as Level 0,
    but also reserves one dedicated disk for error correction data. It provides
    good performance and some level of fault tolerance.
         * Level 4: block-level striping with dedicated parity
         * Level 5: block-level striping with distributed parity
         * Level 6: block-level striping with two sets of distributed parity for extra
    fault tolerance
         * Level 7: Asynchronous, cached striping with dedicated parity
        Configuring Hard Drives
   Most IDE drives have jumpers that select
    the "master" or "slave" role on the
    controller, but modern drives also have a
    "CS" or "Cable select" pin. This allows the
    IDE cable itself to select the drive's role:
    all drives that have the CS jumper set
    allow the cable to choose which device is
    the master and which is the slave.
     Configuring Hard Drives
 When a drive is on the cable alone it
  should be set to Master OR Cable Select –
  providing it is plugged into the end
  connector.
 When there are two drives, the drive that
  should be bootable should be set to
  Master or Cable Select – providing it is
  plugged into the end connector.
      Configuring Hard Drives
 When there are two drives, one that is
  bootable, one that is not; The bootable
  drive should be set to Master or Cable
  Select – providing it is plugged into the
  end connector.
 When there are two drive, both that are
  bootable; They should be both set to
  Cable Select.
Configuring Hard Drives
      IDE / EIDE
         Configuring Hard Drives

   SATA does not require Master Slave settings.
    SATA drops the master/slave shared bus of
    PATA, giving each device a dedicated cable and
    dedicated bandwidth. While this requires twice
    the number of host controllers to support the
    same number of SATA devices
            Partitioning A Hard Disk
   Primary Partitions:
    A primary partition may contain an operating system along with any number of data
    files (for example, program files, user files, and so forth). Before an OS is installed,
    the primary partition must be logically formatted with a file system compatible to the
    OS.

   If you have multiple primary partitions on your hard disk, only one primary partition
    may be bootable and active at a time. The active partition is the partition from which
    an OS is booted at computer startup.

   Primary partitions other than the active partition are hidden if their file system type is
    not recognized, preventing their data from being accessed. Thus, the data in a
    primary partition can be accessed (for all practical purposes) only by the OS installed
    on that partition.

   If you plan to install more than one operating system on your hard disk, you probably
    need to create multiple primary partitions; most operating systems can be booted
    only from a primary partition.
          Partitioning A Hard Disk
   Extended Partitions:
    The extended partition was invented as a way of getting
    around the arbitrary four-partition limit. An extended partition
    is essentially a container in which you can further physically
    divide your disk space by creating an unlimited number of logical
    partitions.

   An extended partition does not directly hold data. You
    must create logical partitions within the extended partition
    in order to store data. Once created, logical partitions
    must be logically formatted, but each can use a different file
    system.
        Partitioning A Hard Disk
   Logical Partitions

   Logical partitions may exist only
    within an extended partition and are meant
    to contain only data files and operating
    systems that can be booted from a logical
    partition (for example, Linux, Windows NT,
    and so forth).
             Formatting A Hard Disk
   Formatting a hard disk arranges the magnetic media in a pattern so that the
    operating system knows where it is in relation to the data on the disks
    surface

   When doing a clean install of Windows XP, after you’ve selected the
    partition where XP will be installed, you are presented with the option to
    format the drive or partition. The format options are:

        Format the partition using the NTFS file system (Quick)
        Format the partition using the FAT file system (Quick)
        Format the partition using the NTFS file system
        Leave the current file system intact (no changes)

   The difference between the regular format versus the quick format is
    whether or not the volume is scanned for bad sectors using the chkdsk
    command. Both methods remove the files from the volume.
                   Format Choices
   FAT16
   The FAT16 file system was introduced way back with MS–DOS in
    1981. It was designed originally to handle files on a floppy drive, and
    has had minor modifications over the years so it can handle hard
    disks, and even file names longer than the original limitation of 8.3
    characters, but it's still the lowest common denominator.
   The biggest advantage of FAT16 is that it is compatible across a
    wide variety of operating systems, including Windows 95/98/Me,
    OS/2, Linux, and some versions of UNIX. By default many of these
    OS’s can read FAT16!
   The biggest problem of FAT16 is that it has a fixed maximum
    number of clusters per partition, so as hard disks get bigger and
    bigger, the size of each cluster has to get larger. In a 2–GB partition,
    each cluster is 32 kilobytes, meaning that even the smallest file on
    the partition will take up 32 KB of space. FAT16 also doesn't support
    compression, encryption, or advanced security using access control
    lists.
                   Format Choices
   FAT32
   The FAT32 file system, originally introduced in Windows 95 Service
    Pack 2, is really just an extension of the original FAT16 file system
    that provides for a much larger number of clusters per partition. As
    such, it greatly improves the overall disk utilization when compared
    to a FAT16 file system.

   However, FAT32 shares all of the other limitations of FAT16, and
    adds an important additional limitation—many operating systems
    that can recognize FAT16 will not work with FAT32—most notably
    Windows NT, but also Linux and UNIX as well.

   Now this isn't a problem if you're running FAT32 on a Windows XP
    computer and sharing your drive out to other computers on your
    network—they don't need to know (and generally don't really care)
    what your underlying file system is.
                   Format Choices
   NTFS

   The NTFS file system, introduced with first version of Windows NT,
    is a completely different file system from FAT. It provides for greatly
    increased security, file–by–file compression, quotas, and even
    encryption. It is the default file system for new installations of
    Windows XP.

   There are DOS and Legacy Windows drivers to allow older systems
    to read NTFS. Unix/Linux also has a NTFS driver, so these OS’s
    can read NTFS partitions.
         Hard Drive Maintenance
   Chkdsk
       If your Windows operating system experiences a
        problem, you can use the Chkdsk disk repair utility
        included in the operating system to check the file
        system on each logical partition and check the disk
        surface for unreadable or corrupted sectors.

       The Chkdsk utility creates and displays a status
        report for a disk based on the file system used.
        Chkdsk also lists and corrects errors on the disk. You
        can run Chkdsk from your Windows operating
        system. If you cannot start your operating system
        because of the problem, you can run Chkdsk from the
        Windows Recovery Console.
        Hard Drive Maintenance
   CleanMGR
     Cleanmgr.exe is designed to clear
      unnecessary files from your computer's hard
      disk. You can configure Cleanmgr.exe with
      command-line switches to clean up the files
      you want. You can then schedule the task to
      run at a specific time by using the Scheduled
      Tasks tool.
     It is important to clean your disk of
      unnecessary files BEFORE you defrag it!
         Hard Drive Maintenance
   Sometimes when you install a program or create a data file, the file
    ends up chopped up into chunks and stored in multiple locations on
    the disk. This is called fragmentation.

   There's a simple solution to file fragmentation: use Windows Disk
    Defragmenter (Start –> Programs –> Accessories –> System Tools
    –> Disk Defragmenter). This utility, commonly called Defrag, gathers
    all the scattered file fragments and writes them into adjacent
    clusters, so each file occupies a contiguous section of the disk.

   Defrag works by moving slabs of data to unused parts of the disk, in
    order to open up a large free section of space. It then assembles the
    fragmented parts of a file and writes them in one complete piece to
    the cleared space; it then does the same with the next file; and so
    on until the entire disk is defragmented.
         Hard Drive Maintenance
   Defrag Limitations
       Defrag cannot defragment open files or
        Operating System Files that are in use.
   To over come this limitation you can use
    specialty software programs.
     Pagedfrg – is a utility to defragment the
      pagefiles
     Contig – is a utility to defragment individual
      files.
Questions


				
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