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CompTIA® A+™ Core 2 Exam Notes :Troubleshoot Hard Drives And Raid Arrays With Appropriate Tools

11. The inverter board is responsible for converting low voltage DC power to high voltage AC, necessary to light up the back-light bulb. If the inverter board is bad, the LCD screen (back-light bulb) will not light up when you turn on the laptop, but you still should be able to see a very dim image on the screen.

12. The most likely cause for excessive paging is insufficient Memory. Increase the physical Memory on your computer.

13. Date and Time Not Set is the most common error that occurs when the BIOS battery is drained. You need to replace the CMOS battery.

14. The most likely cause for sporadic movement of mouse is dirt. If dirt has entered the mouse, clean the dirt with IPA, or cotton wetted in soap water.

15. The most likely problem is conflicting IRQs. Since the mouse is working until the modem is used, the IRQ/IO address of modem may be conflicting with that of the mouse.

16. The motherboard displayed has the following expansion slots:

  1. a. PCI slots : 5 (distinguished by white color, usually the number of PCI slots available on a motherboard varies from 3 to 6)

  2. b. ISA slots: 2 (distinguished by black color, longer than PCI slots, placed next to PCI slots.)

  3. c. AGP slot: 1 ( The single slot, next to 5 white PCI slots is AGP slot in brown color. Note that there will be only one AGP slot)

17. To obtain BIOS string ID:

  1. a. Power off the system

  2. b. Either unplug your keyboard or hold down one of the keys on the keyboard

  3. c. Power-on the system and you should get a keyboard error

  4. d. The string in the lower left hand corner of your computer screen represents the BIOS String ID.

18. It is also possible to read the BIOS information by going to the BIOS set-up of the PC by pressing appropriate key (usually Del key) during boot up.

19.Various POST (Power On Self Test) error codes and their description is as below:

  1. Code 01: Undetermined problem

  2. Code 02: Power Supply error

  3. Code 1xx: System board errors

  4. Code 2xx: Memory (RAM) errors

  5. Code 3xx: Keyboard errors

  6. Code 6xx: Diskette Drive errors

  7. x is any single digit integer.

20. The following are true about backup:

  1. a. Full backup: Here all files that have been chosen for backup are backed up, irrespective of whether the archive bit is set or not set. Archive bit is set (ON) after backup.

  2. b. Incremental backup: Here only the files that have been created or have changed since the previous full or incremental backup will be backed up. The archive bit is set after a file is backed up.

  3. c. Incremental backup will backup files that have changed since previous full or incremental backup.

  4. d. Differential backup: Here, the files that have changed or created since the last full backup will be backed up. Note that, unlike Incremental backup, the archive bit is not set on a differential backup. The result of this is that the next differential backup will include files that were backed up during earlier Differential backups.

21. UPS usually contains a filter to smoothen the noise, and this filter is called noise filter.

4.3 Given a scenario, troubleshoot hard drives and RAID arrays with appropriate tools

1. If the CMOS setup is not properly setup the computer may ignore or not look at the CD-ROM as a bootable option. Verify in the CMOS that your settings are properly set to boot from the CD-ROM drive.

2. The Complementary Metal-Oxide Semiconductor (CMOS) allows the computer to store the Real Time Clock (RTC)and other device information even after the computer is switched off and on. This is achieved by using a battery just for CMOS.

3. Generally, these settings will be under the boot options. Setup your boot options similar to the below example.

  1. 1 - Floppy / LS120

  2. 2 - CD-ROM

  3. 3 - Network (if available)

  4. 4 - Hard Disk Drive

4. If CD-ROM is listed after a device that is bootable it will boot from the other device before the CD-ROM. Verify that the devices before CD-ROM, such as floppy, do not have bootable media in them.

5. If the SCSI bus termination is not done, SCSI devices on the bus will not function properly. This is due to reflection of the signals at the end of the bus. To prevent this, both ends of the SCSI bus needs to be terminated. If one end of the SCSI bus is terminated, you may find intermittent problems. Never terminate the bus at a device connected in between.

6. If you are creating a Striped volume on a new Windows 2000 machine, it can only be created on dynamic disks. However, if you are upgrading a Windows NT computer to Windows 2000, any existing stripe set will be supported.

7. If you are finding that the Logical Disk > %Free Space counter is less than 10%, you might need to make additional free space available. This can first be done cleaning up the disk of any unwanted files, duplicate files etc. If required, additional physical disk may be provided.

8. Some of the important System Monitor counters are:

  1. a. Memory>Available Mbytes: measures the amount of physical memory that is available. Typically > 4MB. If less than 4 MB, consider adding more memory.

  2. b. Memory>Pages/Sec: Shows the number of times that the disk has been accessed, because requested information was not available in memory. If the value of the counter is not below 20, you should add more memory. A value of 4 or 5 is typical.

  3. c. Paging File>%Usage: Indicates the % of allocated page file utilization. Should be less than 99%.

  4. d. Processor>%Processor Time: measure the time that the processor is busy. Should be typically less than 80%

  5. e. Processor>Interrupts/Sec: Indicates the average number of hardware interrupts that the processor receives each second. If more than 3,500, you can suspect a program or faulty hardware.

  6. f. PhysicalDisk>%Disk Time: Measures the amount of time that the physical disk is busy servicing read or write requests. If more than 90%, you can improve the performance by adding another disk channel.

  7. g. PhysicalDisk>%Current Disk Queue Length: indicates the number of pending disk requests that need to be processed. The value should be less than 2. The disk problems might arise from less memory, resulting in usage of excessive paging. Ensure that the memory is sufficient before attending to the disk problem.

8. LogicalDisk > %Free Space counter: Indicates the amount of logical disk's free disk space. Typical value is 10% or above.

9. If you have a standard desktop PC that uses integrated drive electronics (IDE) disk drives, then these will be detected during setup. If, however, you use SCSI disks or have Redundant Array of Independent Disk (RAID) storage systems, you will see, shortly after the reboot, the following line of text displayed at the bottom of the screen:

10. "Press F6 if you need to install a third party SCSI or RAID driver..." Pressing F6 will start a dialog that allows you to configure and install the drivers for your SCSI or other disk subsystem controllers. This option is usually used on server platforms that use large-capacity, high-speed, fault-tolerant disk subsystems. For most PCs, however, you won't need to use this option.

11. If you want to format a drive and also make it bootable, you need to format with /s switch. By issuing this command, the boot files IO.SYS, MSDOS.SYS, COMMAND.COM get copied to the disk.

12. Important RAID (Redundant Array of Inexpensive Disks) details are given below:

  1. a. RAID 0: This has striping but no redundancy of data. It offers the best performance but no fault-tolerance.

  2. b. RAID 1: This is also known as disk mirroring. It consists of two or more drives that duplicate the storage of data. There is no striping. Read performance is better since either disk can be read at the same time.

  3. c. RAID 2: It uses disk striping across disks with some disks storing error checking and correcting (ECC) information. RAID 2 is hardly used because it is expensive and does not provide fault tolerance like other forms of RAID levels.

  4. d. RAID 3: It uses disk striping and dedicates one drive to storing parity information. The embedded error checking (ECC) information is used to detect errors.

  5. e. RAID 4: Block-level striping with dedicated parity. RAID-4 offers no advantage over RAID 3

  6. f. RAID 5: Uses block-level striping with distributed parity. Thus, all read and write operations can be overlapped. RAID-5 stores parity information but not redundant data (but parity information can be used to reconstruct data). RAID 5 requires at least three disks for the array. It's suitable for multi-user systems in which performance is not critical.

13. It is obvious that you can get shock is due to sudden discharge of static electricity. Since the operator is touching the memory module when the discharge happened, it is most likely that the memory module may have internally damaged. This damage may or may not show up immediately. In any case, it always recommended to replace the statically damaged module with a good one. Follow anti-static precautions before touching any electronic components inside a PC.

15. If the hard-disk is making sound, the most likely problem is that the hard disk read/write head is scratching the disk surface. It often results in the total failure of the disk. If you find that you can still read/write to the disk, backup the hard disk and replace immediately.

16. Low level formatting will erase the data on a hard drive permanently.

17. A hard disk should never be low level formatted at the customer premises. It is highly recommended that it is done at the manufacturer's or at any authorized center.

It is very cumbersome to change the partition sizes, once the hard disk is partitioned and used. It may require backing up all the data and restoring after repartitioning.

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