HEAD CRASH

What is head crash???

A serious disk drive malfunction. A head crash usually means that the head has scratched or burned the disk. In a hard disk drive, the head normally hovers a few microinches from the disk. If the head becomes misaligned or if dust particles come between it and the disk, it can touch the disk.

When this happens, you usually lose much of the data on the hard disk and will need to replace both the head and the disk. For this reason, it is important to operate disk drives, particularly hard disk drives, in as clean an environment as possible. Even smoke particles can cause a head crash.

A head crash in a modern drive. Note circular mark on the platter.

For more detailed information, you can go to http://en.wikipedia.org/wiki/Head_crash

                                                                    http://en.wikipedia.org/wiki/Hard-disk_failure

A Hard Drive Crash Can Be Bad... Trying To Fix It Yourself Can Be Worse !!!

We rely on our computers more than ever, and when a hard drive crash occurs, years of data can be gone in the blink of an eye. In most cases the data is fully recoverable, but there are some common mistakes people make when attempting to do the job themselves.

If you experience a hard drive crash, it doesn't take much to make a bad situation even worse. In the event of a hard drive crash, in most instances, the data is completely recoverable at first. However, as part of human nature, we often try to avoid the high costs associated with hard drive data recovery in order to find some sort of "quick fix" to a very serious problem. In this report we will go over some of the symptoms of a hard drive crash and the things you can try in the event of a suspected hard drive crash, along with things you should avoid.

 

What Noise Is The Drive Making???

The first thing to take into account is whether or not the hard drive is making any unusual noises. Often times when there is a problem with the read/write head within the drive or a firmware issue in the logic board a "clicking" sound will be heard. If this is the case, then you should immediately power down the system and refrain from reapplying power. Same thing goes for any unusual sound, whether it's grinding, squealing, our sounds like a "laser gun". If any of these occur you should immediately power the system down, just pull the plug from the wall.

Unfortunately in the situations listed above, there is little that you can do to recover the data yourself. Actually, unless you have a clean room, fully equipped with the right tools and a trained technician there is nothing that can be done. Even hard drive manufacturers avoid this line of work, and many who do offer data recovery services are only sub-contracting the work out to an established data recovery firm.


Never Ever Open Your Hard Drive !!!
 If the data on a hard drive has even the most minimal value to you, then it is imperative that you do not open the drive. Data recovery companies often get calls or e-mails from people who felt they had the right equipment and know-how to perform something as serious as a head replacement. Once they've removed the hard drive's protective case, more often than not, the damage is irreparable.


Working with the internal components of a hard drive requires at least a Class-100 clean room. A clean room does not mean a room that you just vacuumed and dusted (believe it or not people say that to us all the time). A clean room is a special work area in which air quality is heavily controlled and it is vital to hard drives during the manufacturing or assembly process.

 The air in the room is regulated in term of air particles, temperature and humidity. A Class-100 clean room means there exists no more than 100 particles that are larger than 0.5 microns in one cubic foot of air. Opening a hard drive in air meeting anything less than the standard listed above will mean certain death for your hard drive and any data contained therein.


The Freezer Method

There has been a long running myth about putting your hard drive in the freezer when it crashes in order to revive it just long enough to pull your data off of it. ACS Data Recovery has run this test for fun on many occasions in different scenarios with junk test drives that they have in the lab.

So far they have yet to see this actually produce any positive results. In fact, in one instance they actually began to see the formation of tiny microscopic ice crystals on the platter themselves, which is a definite crash waiting to happen.
See the problem with this theory is, drives are not completely sealed.

Regardless of what you've heard or read, all hard drives have a tiny breather hole (usually marked with a label that says "do not cover"). This hole not only aids in cooling but it also helps to equalize air pressure in the drive when the platters are spinning. On the other side of this hole is a filter, which keeps dirt and debris from getting inside the drive.

However, this filter does not stop heavy amounts of moisture (especially in flood situations) or moisture vapor (such as found in a freezer). This moisture vapor has been known to settle on the platters and when a system is powered up, the read/write head would resemble an airplane flying into a mountain.

For more infomation, you can surf to tis website~ http://www.beststuff.com/computers/a-hard-drive-crash-can-be-bad-trying-to-fix-it-yourself-can-be-worse.html 

http://www.ibas.com/espana/noticias/pictures

http://www.youtube.com/watch?v=PoVBHG4kajA&feature=related

Citation :

1. http://www.howstuffworks.com/question60.htm
2. http://www.webopedia.com/TERM/H/head_crash.html
3. http://en.wikipedia.org/wiki/Head_crash
4.  http://en.wikipedia.org/wiki/Hard-disk_failure
5. http://www.beststuff.com/computers/a-hard-drive-crash-can-be-bad-trying-to-fix-it-yourself-can-be-worse.html 



CHAPTER 8 = SECONDARY STORAGE

  SOLID-STATE STORAGE 

• Solid-state storage is a nonvolative, removable storage medium that employs integrated circuits (ICs ) rather than magnetic or optical media.
•  It is the equivalent of large-capacity, nonvolatile memory.  
• Examples include flash memory Universal Serial Bus (USB) devices and various proprietary removable packages intended to replace external hard drives.   
• Solid-state storage media lags behind electromechanical drives in terms of storage capacity.  
• Solid-state storage devices have no moving parts and are more reliable and require less power than hard disks. 
• For more information about solid-state storage refers to http://en.wikipedia.org/wiki/Solid-state_drive  

                                                        
                                          http://viroptics.pancamo.com/2008/01/bitmicro-832gb-solid-state-soft-drive.html  


 FLASH MEMORY  

• Flash memory refers to a particular type of EEPROM, or Electronically Erasable Programmable Read Only Memory.  
• It is a memory chip that maintains stored information without requiring a power source.  
• It is often used in portable electronics, like MP3 players, and in removable storage devices. 
• Flash memory differs from regular EEPROM in that EEPROM erases its content one byte at a time. 
• Flash memory can erase its data in entire blocks, making it a preferable technology for application that require frequent updating of large amounts of data as in the case of a memory stick. 
• Flash memory is used in digital media players like the iPod to store and play music and video files. 
• Flash memory is also used to store images captured from digital cameras and then to transfer the images to desktop and other computers.  
• For more information about flash memory can refers to http://www.wisegeek.com/what-is-flash-memory.htm   

                                         
                               http://www.blendsblog.com/guide/what-is-flash-memory/  
                                          

USB DRIVES DRIVES

• A USB flash drive consists of a flash memory data storage device integrated with a USB (Universal Serial Bus ) interface. 
• USB flash devices are typically removable and rewritable and physically much smaller than a floopy disk. 
• They are smaller, faster, have thousands of times more capacity, and are more durable and reliable because of their lack of moving parts.
• There are typically four parts to a flash drive:   

1. Male type-A USB connector – provides a physical interface to the host computer. 
2. USB mass storage controller – implements the USB host controller. The controller contains a small microcontroller with a small amount of on-chip ROM and RAM. 
3. NAND flash memory chip – stores data. NAND flash is typically also used in digital cameras. 
4. Crystal oscillator  – produces the device's main 12 MHz clock signal  and controls the device's data output through a phase-locked loop.    

• Advantages of USB Drives : 

1. Data stored on flash drives is impervious to scratches and dust, and flash drives are mechanically very robust making them suitable for transporting data from place to place and keeping it readily at hand. 
2. Flash drives implement the USB mass storage device class so that most modern operating systems can read and write to them without installing device drivers.   

• Disadvantages of USB Drives : 

1. USB flash drives do not include a write-protect mechanism, although some have a switch on the housing of the drive itself to keep the host computer from writing or modifying data on the drive. 
2. USB flash drives are more expensive per unit of storage than large hard drives, but are less expensive in capacities of a few tens of gigabytes as of 2011. 

• For more information refers to http://en.wikipedia.org/wiki/USB_flash_drive  

                                          
                             http://www.engadget.com/2004/10/18/one-128mb-tomago-kudasai/
Citation :

• http://en.wikipedia.org/wiki/Solid-state_drive 
• http://www.wisegeek.com/what-is-flash-memory.htm 
• http://en.wikipedia.org/wiki/USB_flash_drive  
• Computing Essentials Complete 2010     

CHAPTER 8 = SECONDARY STORAGE

SECONDARY STORAGE 

•        Secondary storage devices are used to save, to back up, and even to transport files consisting of data or programs from one location or computer to another. 

•        Secondary storage devices have always been an indispensable element in any computer system.

•         Secondary storage provides permanent or nonvolatile storage.

•       Some important characteristics of secondary storage include:

1.     Media are actual physical material that holds the data and program.

2.     Capacity measure how much a particular storage medium can hold.

3.     Storage devices are hardware that reads data and programs from storage media.

4.     Access speed measure the amount of time required by the storage device to retrieve data and program. 

 

HARD DISKS

• A hard disk drive (HDD) is a non-volatile , random access device for digital data. It features rotating rigid platters on a motor-driven spindle within a protective enclosure. Data is magnetically read from and written to the platter by read/write heads that float on a film of air above the platters. 

• Introduced by IBM in 1956, hard disk drives have fallen in cost and physical size over the years while dramatically increasing in capacity. Hard disk drives have been the dominant device for secondary storage of data in general purpose computer since the early 1960s. They have maintained this position because advances in their areal recording density have kept pace with the requirements for secondary storage. Today's HDDs operate on high-speed serial interfaces; i.e., serial ATA (SATA) or serial attached SCSI  (SAS).           

Components  

• A typical hard disk drive has two electric motors; a disk motor to spin the disks and an actuator (motor) to position the read/write head assembly across the spinning disks.

• The disk motor has an external rotor attached to the disks; the stator windings are fixed in place.   

• For more information refers to http://en.wikipedia.org/wiki/Hard_disk_drive     

INTERNAL HARD DISK   

• It is located inside the system units. 
• The are designated as C drive. 
• Are able to storage and retrieve large quantities of information quickly. 
• Used to storage program and large data files.                                                
    
   
  http://www.blogger.com/goog_227295440
  
  
  EXTERNAL HARD DRIVE     
  • Provide fast access, they have a fixed amount of storage and cannot be easily removed from the system cabinet. 
  • Typically connect to a USB or FireWire port on the system unit, are easily removed and effectively provide an unlimited amount of storage. 
  • For desktop computers have typically capacities of 20 to 500 GB. 
  •   Credit card-size hard disks cartridges called PC Card hard disks are available for notebook computers with typically capacities up to 5 GB.

 

http://www.build-your-own-computer.net/external-hard-drive.html

Secondary storage are important because can be used to restore a backup of your files if you have to format. It also can be bring it with you if you need to access files at work or somewhere else. Without secondary storage you would lose all of you data every time your computer powered down. In order words , your computer would not have anywhere to save data indefinitely. For more information you can refers to http://wiki.answers.com/Q/Why_secondary_storage_devices_are _important.                                                                                                                            

Citation ~ http://wiki.answers.com/Q?Why_secondary_storage_devices_are_important.       

~http://en.wikipedia_org/wiki/Hard_disk_drive                                       

~Computing Essentials 2010 Books