Disk failures and facts on hard disk drives

[siopao1984]

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No one anticipates a hard drive crash and while a data loss incident can be a very emotional time for anyone who values the data or has the responsibility of safeguarding it well being. A company’s entire digital portfolio or person’s lifetime of hard work may be in the balance between a successful data recovery attempt and a failed attempt. The proper implementation of data recovery techniques is a methodical and delicate practice. Attempting to apply data recovery techniques while in an emotional state or without the proper training is a recipe for disaster.

Anatomy : Hard disk drive

To understand more about severity of disk failure, a closer look at disk will help diagnose the problem at hand. A hard disk drive is the device used to store large amounts of digital information in computers and related equipment like iPods and games consoles such as the Xbox 360 and PS3.

A typical hard disk drive consists of a motor, spindle, platters, read/write heads, actuator and electronics.



Platters A hard disk has one or more platters - or disks - and each platter usually has a head on each of its sides. In modern drives the platters are made from glass or ceramic. The platters themselves are non-magnetic but have a magnetic coating which holds the magnetic impulses which represent the data. A typical hard drive will have three or four platters and modern varieties can hold 20GB per disk.

Read/Write head The read/write heads float on a cushion of air only nanometers above the surface of the platters. As the read/write heads pass over the spinning platters they magnetize the surface in a pattern which represents the data in digital form. The data is stored digitally as tiny magnetized regions, called bits, on the disk.A magnetic orientation in one direction on the disk could represent a "1", while an orientation in the opposite direction could represent a "0".Data is arranged in sectors along a number of concentric tracks. These tracks are arranged from the inner diameter of the disk to its outer edge. When reading data on a disk, a similar process occurs in reverse.

Spindle The platters are mounted on the spindle which is turned by the drive motor. Most current hard disk drives spin at between 5,400 and 10,000 RPM.Modern hard drives can transfer 80 megabytes of data per second.

Head arm The triangular-shaped head arm holds the read/write heads and is able to move the heads from the hub to the edge of the drive. There is one hard arm per read/write head and all of them are lined up and mounted to the acuator as a single unit.

Voice coil actuator The head arm is controlled by an actuator - which has to be incredibly accurate. 30,000 tracks can be stored within one inch of space on a platter. The hard disk's electronics control the movement of the actuator and the rotation of the disk, and perform reads and writes on demand from the disk controller via its interface to the computer.

Air filter Hard drives are typically air-sealed to enable the heads to float and to avoid contamination from dust. The air inside the the hard drive enclosure is in constant motion and passes through the filter to remove any leftover contaminants from the manufacturing process and any particles or chemicals that may have somehow entered the enclosure.

[siopao1984]

The methods discussed here have proven successful for thousands of data recovery incidents. Many recovery methods rely heavily on proper diagnosis of the problem(s) affecting the hard drive. If the wrong diagnosis is made and the wrong method of data recovery is applied, total and permanent data loss is inevitable.



Physical Failures:

A physical failure is any time a drive can not be accessed because of electronic malfunction or internal hardware failure.

These failures can result in the drive not being recognized by the computer’s BIOS or operating system, as well as repetitious clicking or grinding noises. If you hear any unusual sounds coming form your drive, power off your PC and don’t attempt to use it again until you can have your hard drive sent to a recovery center.

The noises you are hearing could indicate a head crash. A head crash happens with the arms that read the data on the surface of your hard drive’s platters smash into the rotating platter instead of gliding across it on a cushion of air like they are supposed to. This results in physical damage to that pltters and can cause a complete and permanent data loss.

The only way to recover from a physical failure is to either replace the damaged hard drive component or move the data platters to a donor drive where they can be recovered to a stable destination drive. This process requires special handling and the use of a cleanroom.

Hard drive does not get detected. If the computer does not detect the hard drive, or the computer just does not want to turn on when the hard drive is connected to it, you might have a bad hard drive board. This is the big circuit board located at the bottom of your drive. PCB boards tend to get damaged over time due to the heat generated by the hard drive itself.

Hard drive gets detected but data is inaccessible. Hard drive gets detected by Windows and can be accessed but you do not see any data inside, or you get a message saying that the drive needs to be formatted. You probably have a corrupted file system in you hands. Data may sometimes in this case shows as 0 bytes. Formatting may not be an option in the circumstances and data recovery softwares readily availble in the market will no longer be able to read/write the disk surface. Printed circuit board/ data controller chips failure is likey in theses cases. Commmonly available drives can be repaired in these cases.

Hard disk drive displays no sign of power and/or no sound of the drive "winding up". It is not all too uncommon for a logic board component to begin to smolder and burn. There are several reasons for this, such as sudden increase of power or a failure of a power regulator to function properly. In most cases, it is possible to see the location on the logic board which has received the damage.

Hard disk drive powers up & then spins constantly with a loud winding sound. Hard drive unit powers up and appears to spin out of control. The drive may or may not mount. If it does mount, it will most likely be sporadic in successful operation. This symptom is often indicative of a severe power regulation failure. The symptom could also be caused by a component malfunction within the drive.

Hard drive powers up and then winds down, non-responsive. The hard disk drive will power up, you can hear the unit wind up and then it suddenly powers down. The unit may or may not power up again. It would not be uncommon for a hard drive in this condition to function for a period of time and then fail again. It is likely that a drive in this condition has suffered from an inconsistent power feed. Low or inconsistent power supply can often cause more damage than an over power supply or surge.

Hard drive unit emits an OCCASIONAL clicking sound. This is very common and often an overlooked sign of imminent drive failure. One of the locking points for the Cam/Actuator arm has malfunctioned and the arm swings overly wide, causing it to smack against the inner drive unit housing or stop block, which is usually made out of plastic. The drive most likely works and the volume is mounted and functioning perfectly. This condition promotes a false sense of security and will often cause a user to ignore the obvious warning signs. Drive in this case can be repaired however, a replacement is strongly recommended.

Hard drive unit emits a CONSTANT clicking sound. Hard drive's read write head/actuator arm has likely broken from its locking points and is swinging freely within the drive or swinging wide. This can also be caused by failure of the servo motor. The drive likely does not mount and appears not to function accept for the loud clicking sound. In this state, the drive is unable to read or write, to or from, the digital media on the drive platter. Please STOP using this device immediately and send it for data recovery. Head/Platter replacement and then using data recovery equipment to read data is the most likely solution in this case.

Hard drive unit powers up, but the drive does not mount, and there is no discernable data read/write sound. This condition is often caused by overheating and occurs when excessive heat causes one or more of the inner components to expand and stick to another component or to the housing unit itself. This condition will cause the drive to stop reading or writing data. It is not uncommon for the unit to show up as a mounted drive under windows when this condition exists, however; no folders or files will be displayed. A prompt to format the drive may even be displayed, but the system will most likely lock up when attempting to access the volume.

Hard drive powers up and a scraping sound is audible. Read/write head or arm has broken or come loose and is scraping the digital media on the drive platter(s). STOP using this drive immediately. The scraping sound is the read/write heads impacting with the drive platter. The read/write heads are scraping the magnetic media from the drive platter and throwing debris all about the inner drive housing unit, increasingly compounding the problem. If this condition just occurred, and little damage has taken place to the drive patter's digital magnetic media, it is possible to remove the broken read/write arm and replace it with a known good arm. Extensive and delicate cleanup will be necessary in order to remove the debris from the drive platters and drive housing unit. Data recovery rates dealing with this type of symptom are very low. Head/Platter replacement and then using data recovery equipment to read data is the most likely solution in this case.

Hard drive has been exposed to water damage. You have a hard disk drive that has been immersed in or otherwise exposed to water. Even if the drive has been removed from the water and appears to be dry, do not attempt to power the drive up. If the drive was running at the time of exposure, it is possible that the logic board has been damaged beyond repair. All hard drives have ventilation ports, they are small and usually regulated by a flap type of control that allows air to escape, but does not allow for dust and debris to enter. Chances are good that this flap prevented water from entering the drive housing unit and reaching the digital media on the drive platters. It is possible, under controlled conditions, to properly dry the remaining and unseen moisture on the drive, replace the logic board, and recover data. To increase your probability of data recovery, and decrease your risk of damaging or contaminating the logic board during handling or removal, deliver the drive to a data recovery specialist immediately. Platter replacement and then using data recovery equipment to read data is the most likely solution in this case.

Hard drive unit has been exposed to fire. Hard drive has been damaged by fire. The most delicate portions of the drive have likely been melted or damaged to some degree. Many individuals simply call it a lost cause at this point but not so fast, there is still hope. This drive is in serious need if examination by a professional data recovery expert. Attempts to replace the logic board and power the unit up could cause an increase in damage. Metal expands when exposed to heat. It sometimes contracts when it cools down, but there is no guarantee. A data recovery expert may be able to manipulate the drive, replacing parts where necessary and even removing the platters for successful data recovery. Platter replacement and then using data recovery equipment to read data is the most likely solution in this case.

[siopao1984]

Logical Failures

In the event of a logical failure the hard drives electronic components and mechanical components are all working properly. Logical failures occur as a result of defective media (bad platter) or data corruption from another source (destroyed file table, etc…)

In the most extreme cases logical failure can include a hard drive that spins up fine, but is not recognized by the computer’s BIOS as being present. Some times, the computer’s BIOS can see your hard drive, but for some reason can not access the data on it. It may not be able to mount the partition or Windows may simply report that no drive is present at all.

Almost all logical failures can be recovered without the need to open the hard drive. While there are a number of logical data recover software programs on the market, its important to know why your drive has experienced a logical failure before you attempt to recover your data. If you misdiagnose a logical failure, you can cause irreparable damage to the drive in your recovery attempt.

Advanced recovery Disk imaging and cloning then sector by sector scan of afftected drive is used and all recoverable media copied to a client drive.

Deleted file recovery Files deleted from system drives and backup drives can be recovered. Files deleted from Recycle bin are also recovered via this method. If the file size is smaller than the cluster size (clusters are commonly 32 KB, but it varies with drive size) you should get a 100% recovered file as you do not actually need the FAT entry. Larger files are usually allocated in consecutive clusters, and most data recovery software assumes this when it rebuilds files without a FAT entry. This will work for most types of files, but runs into problems with files that grow over time. Files like this are invariably fragmented, allocating consecutively is impossible due to other files taking the intermediate clusters. There are some important files that fall into this category, such as Databases, Email files, large text documents, and directories.

Formatted recovery Formatted drives and partitions that may have lost/damaged file system Accidental file deletion, formatting, or partition deletion can result in a missing File Allocation Table entry.

RAW recovery File system data structures of a drive have suffered serious corruption or overwriting and data recovery software cannot scan such drives. Deleted File Recovery, Complete Recovery cannot locate missing / lost files and folders. Files were deleted "long back" and cannot be identified because of over-writing to file system data structures. Recently deleted files are not recovered because of severe fragmentation. This is a common problem in FAT file system drives. RAW file recovery can discover such deleted files and folders from the temporary copies created by the application software and/or the operating system. RAW File Recovery scans every sector of your storage media for the lost files that you wish to recover and displays them in a tree according to the file type. The software scans the drive in RAW mode and can locate the files without the aid of file system data structures. It recognizes and restores many file types. This includes word processor, document, spreadsheet, graphic, internet, multimedia, source code and many such file formats. The list of file types can be viewed and selected in the software. As data is recovered bypassing file systems, folder/file structure is lost and as a result recovered files will have numerical names as opposed to file's original names.

File repair services Corrupted data recovered during any of the above means can be then processed and repaired. Files of EXCEL, ACCESS, POWERPOINT, WORD, ZIP, RAR, OUTLOOK EXPRESS AND MS OUTLOOK can undergo such repair process.

[siopao1984]

What should you avoid:

We can never emphasise enough on this, so please,

DO NOT, whatever the problem is, take the enclosure apart Hard drives are assembled in clean rooms (cleaner than surgical rooms) and then sealed. Hard drive platters spin at a rate of 4,200 to 10,000 rotations per minute. Opening the hard disk drive to inspect the contents, by anyone but properly trained personnel in a controlled environment, could lead to contamination of the magnetic media. Damage can occur because the read/write heads move at a very close distance to the spinning hard drive platters. As the platters spin, it is only a matter of time before the head comes into contact with dust or debris on the platter. At this point, an impact will occur, the surface of the platter containing the magnetic media will become damaged and the data contained within this magnetic media will be lost forever.

DO NOT place drive in the freezer You may be told that putting drive in a thick plastic bag and leaving it in the freezer may get drive working again. Please avoid doing this as there is no evidence that this will work and may cause end up doing more damage than good.

DO NOT restart/shutdown your computer via Windows Always power down your equipment by unplugging the AC adapter and removing the battery. Do not try and restart computer as affected drive may overwrite sectors containing data causing loss of data.

DO NOT plug it into another computer

Although, these are only some of the issues we as a data recoery company have come across, if your drive is experiencing any of these symptoms OR if it is not listed here, please don't hesitate to reply to this thread detailing the cause of the problem and issues experienced