Data rate - The data rate is the number of bytes per second that the drive can deliver to the CPU.

Transcription

1 A+ Guide to Hardware, 4e Chapter 7 Hard Drives Learning from Floppy Drives Floppy drives are an obsolescent technology Replacements: CD drives and USB flash memory Good reasons for studying floppy drive technology Developing support skills for legacy applications Building a foundation for hard drive support skill set How Floppy Drives Work Main memory is organized logically and physically Secondary storage devices are similarly organized Physical storage: how data is written to media Logical storage: how OS and BIOS view stored data How data is physically stored on a floppy disk Two types of floppy disk: 5 ¼ inch or 3 ½ inch Subsystem: drive, 34-pin cable, connector, power cord Formatting: marking tracks and sectors on a disk Magnetic read/write heads read/write binary 1s and 0s Heads attach to actuator arm that moves over surface 3 ways to measure the performance of a hard disk: Data rate - The data rate is the number of bytes per second that the drive can deliver to the CPU. Rates between 5 and 40 megabytes per second are common. (PATA) Seek time - The seek time is the amount of time between when the CPU requests a file and when the first byte of the file is sent to the CPU. Times between 10 and 20 milliseconds are common. Capacity: the number of bytes it can hold Hard Drive The platters - These typically spin at 3,600 or 7,200 rpm when the drive is operating. These platters are manufactured to amazing tolerances and are mirror-smooth

2 The arm - This holds the read/write heads and is controlled by the mechanism in the upper-left corner. The arm is able to move the heads from the hub to the edge of the drive. The arm on a typical hard-disk drive can move from hub to edge and back up to 50 times per second How Hard Drives Work Components of a hard drive: One, two, or more platters (disks) Spindle to rotate all disks Magnetic coating on disk to store bits of data Read/write head at the top and bottom of each disk Actuator to move read/write head over disk surface Hard drive controller: chip directing read/write head Head (surface) of platter is not the read/write head Physical organization includes a cylinder All tracks that are the same distance from disk center Tracks and Sectors on the Drive Tracks on older drives held the same amount of data Newer drives use zone bit recording Tracks near center have smallest number sectors/track Number of sectors increase as tracks grow larger Every sector still has 512 bytes Sectors identified with logical block addressing (LBA) Low-Level Formatting Two formatting levels: Low-level: mark tracks and sectors High-level: create boot sector, file system, root directory Manufacturer currently perform most low-level formats

3 Using the wrong format program could destroy drive If necessary, contact manufacturer for format program Problem: track and sector markings fade Solution for older drives: perform low-level format Solution for new drive: backup data and replace drive Note: zero-fill utilities do not do low-level formats Drive Capacity for Today s Drives The OS reports the capacity of hard drives Accessing capacity data using Windows Explorer Right-click the drive letter Select Properties on the shortcut menu Calculating total capacity if drive is fully formatted Record capacity of each logical drive on hard drive Add individual capacities to calculate total capacity Reporting total capacity (regardless of formatting) Windows 2000/XP: use Disk Management Windows 9x: use Fdisk Hard Drive Interface Standards Several standards exist: Several ATA standards PATA SATA SCSI USB FireWire (also called 1394) Fibre Channel The various standards will be covered

4 The ATA Interface Standards Specify how drives communicate with PC system Drive controller interaction with BIOS, chipset, OS Type of connectors used by the drive The motherboard or expansion cards Developed by Technical Committee T13 Published by ANSI Selection criteria: Fastest standard that the motherboard supports OS, BIOS, and drive firmware must support standard The ATA Interface Standards (continued) Parallel ATA Allows two connectors for two 40-pin data cables Ribbon cables can accommodate one or two drives EIDE (Enhanced Integrated Device Electronics) Pertains to how secondary storage device works Four parallel ATA devices can attach with two cables Serial ATA (SATA) cabling Use a serial data path rather than a parallel data path Types of SATA cabling: internal and external The ATA Interface Standards (continued) DMA (direct memory access) transfer mode 7 modes (0-6) bypassing CPU in transfer of data PIO (Programmed Input/Output) transfer mode 5 modes (0-4) involving CPU in data transfer Independent device timing Enables two drives to run at different speed

5 ATA/ATAPI-6 (ATA/100) breaks the 137 GB barrier Addressable space is 144 petabytes (1.44 x PB) Must have support of board, BIOS, OS, IDE controller The ATA Interface Standards (continued) Configuring parallel ATA drives Each of two IDE connectors supports an IDE channel Primary/secondary channels each support two devices EIDE devices: hard drive, DVD, CD and Zip drives Devices in each channel configured as master/slave Designate master/slave: jumpers, DIP switches, cable Configuring serial ATA drives One ATA cable supports one drive (no master/slave) Use an ATA controller card in two circumstances: IDE connector not functioning or standard not supported Other Interface Standards External USB (Universal Serial Bus) USB 1.1 and USB 2.0 accommodate hard drives A USB device connects to a PC via a USB port IEEE 1394 (FireWire) Uses serial transmission of data Device can connect to PC via FireWire external port Device also attaches to an internal connector Fibre Channel Rival to SCSI Allows up to 126 devices on a single bus SATA Serial Advanced Technology Attachment

6 A computer bus primarily designed for transfer of data between a computer and mass storage devices such as hard disk drives and optical drives. The main advantages over the older parallel ATA interface are Faster data transfer Ability to remove or add devices while operating (hot swapping) Thinner cables that let air cooling work more efficiently More reliable operation with tighter data integrity checks. SATA It was designed as a successor to the Advanced Technology Attachment standard (ATA) Serial ATA adapters and devices communicate over a high-speed serial cable. SATA SATA 1: 1.5 Gbits 150 MB/s Transfer SATA 3: 3.0 Gbits 300 MB/s Transfer SATA 6: 6 Gbits 600 MB/s Transfer Less Power Smaller Footprint Hard Drive Speeds SATA Most newer computers purchased within the last two years accept SATA connections. If your computer cannot accept one of the newer SATA hard drives you can purchase SATA adaptor cards that plug into an empty expansion slot on your computer's motherboard. You can purchase SCSI adaptors as well, so follow these tips to guide your decision. How to Select a Hard Drive Hard drive must match OS and motherboard BIOS uses autodetection to prepare the device Drive capacity and configuration are selected Best possible ATA standard is part of configuration

7 Selected device may not supported by BIOS Troubleshooting tasks (if device is not recognized) Flash the BIOS Replace the controller card Replace the motherboard Installations Using Legacy BIOS Older hard drive standards that may be encountered CHS (cylinder, head, track) mode for drives < 528 MB Large (ECHS) mode for drives from 504 MB GB The 33.8 GB limitation or the 137 GB limitation How to install a drive not supported by BIOS Let the BIOS see the drive as a smaller drive Upgrade the BIOS Replace the motherboard Use a software interface between BIOS and drive Substitute BIOS with ATA connector and firmware Steps to Install a Parallel ATA Drive Components needed: The drive itself 80-conductor or 40-conductor data cable Kit to make drive fit into much larger bay (optional) Adapter card (if board does not have IDE connection) Steps for installing parallel ATA drive: Step 1: Prepare for the installation Know your starting point Read the documentation Plan the drive configuration

8 Prepare your work area and take precautions Steps to Install a Parallel ATA Drive (continued) Steps for installing parallel ATA drive (continued): Step 2: Set the jumpers or DIP switches Step 3: Mount the drive in the drive bay Remove the bay for the hard drive Securely mount the drive in the bay Connect the data cables to the drives (can be done later) Re-insert (and secure) the bay in the case Install a power connection to each drive Connect the data cable to the IDE connector on board Attach bay cover and other connections (if needed) Verify BIOS recognizes device before adding cover Steps to Install a Parallel ATA Drive (continued) Steps for installing parallel ATA drive (continued): Step 4: Use CMOS setup to verify hard drive settings Step 5: Partition and format the drive If installing an OS, boot from Windows setup CD If not, use Disk Management utility or Fdisk and Format Serial ATA Hard Drive Installations No jumpers to set on the drive Each serial ATA connector is dedicated to 1 drive A simpler installation process: Install the drive in the bay (like parallel ATA drive) Connect a power cord to the drive Documentation identifies which connector to use Example: use red connectors (SATA1, SATA2) first After checking connections, verify drive is recognized

9 Installing a Hard Drive in a Wide Bay Universal bay kit: adapts a drive to a wide bay Adapter spans distance between drive and bay Troubleshooting Hard Drives Problems occur before and after installation Problems may be hardware or software related Hardware-related problems will be addressed Problems with Hard Drive Installations CMOS setup does not reflect new hard drive Solution: Enable autodetection and reboot system Error message: Hard drive not found. Reseat the data cable and reboot the PC Error message: No boot device available. Insert bootable disk and restart the machine Error message 601 appears on the screen Connect the power cord to the floppy disk drive Error message: Hard drive not present Restore jumpers to their original state Problems with Hard Drive Installations (continued) Things to check if CMOS setup does not show drive Does your system BIOS recognize large drives? Is autodetection correctly configured in CMOS setup? Are the jumpers on the drive set correctly? Are the power cord and data cable connected? How to Approach a Hard Drive Problem After the Installation Some post-installation problems Corrupted data files A corrupted Windows installation

10 A hardware issue preventing system from booting Preparation steps Start with the end user: conduct an interview Prioritize what you have learned Example: make data backup your first priority Be aware of available resources Examples: documentation, Internet, Technical Support Hard Drive Hardware Problems Causes of problems present during boot: Hard drive subsystem Partition table File system on the drive Files required for the OS to boot Some things to do if POST reveals problem Check the jumper settings on the drive Check the cable for frayed edges or other damage Try booting from another media; e.g. setup CD Check manufacturer Web site for diagnostic software Hard Drive Hardware Problems (continued) Bumps are bad A scratched surface may cause a hard drive crash Data may be recovered, even if drive is inaccessible Invalid drive or drive specification System BIOS cannot read partition table information Boot from recovery CD and check partition table To be covered in later chapters Bad sector errors

11 Problem due to fading tracks and sectors Solution: replace the drive Troubleshooting Floppy Drives and Disks Table 7-4 has two columns One identifies errors occurring before and after boot Another displays troubleshooting tasks Summary Current floppy disks are 3 ½ inch, high-density disks Floppy disk format: 80 tracks, each with 8 sectors Hard drive physical organization: cylinders, tracks, sectors Hard drive logical organization: boot record, file allocation tables, and root directory Secondary storage device communicates with system using a standard, such as ATA or SCSI Summary (continued) Parallel ATA (or EIDE): allows connection of up to 4 devices Serial ATA (SATA): specifies one cable per device SCSI group: allow up to 7 or 15 physical devices and multiple logical devices per physical device Other drive interface standards: USB, FireWire, Fibre Channel Newly installed hard drives are usually automatically detected by BIOS