Describing the General Principles of Data Recovery and Introducing the top Softwares in this Field – Part 2

Data recovery means recovering inaccessible information from any storage media. In this article, we will explain the general principles and introduction

Logical Hard Disk Damage

The term ‘logical damage’ refers to a situation where the error is not a hardware problem and requires software-level optimization solutions.

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If you’ve ever encountered the horrible “Corrupt Hard Drive” error message,

you’re definitely aware of the amount of frustration this message brings.

But there is still hope and lost data can be recovered. If so, if you connect your hard drive to another computer,

You may find that only the operating system is affected and that the rest of the data is in good health.

So you can simply fix the problem by copying its healthy data to another healthy hard drive.

Media errors, file systems, and faulty partitions

In some cases, data on the hard drive may be unreadable due to damage to the partition table,

file system, or intermittent media errors.

In most cases,

at least part of the original data can be recovered through proprietary data recovery software

such as Testdisk by repairing the damaged partition table or file system.

Software such as GNU Ddrescue is able to recover from multimedia files and raw data even

with occasional errors when the file system or partition table is damaged.

This type of data recovery can be performed by users with no hardware drive expertise

and without the need for specialized physical equipment or access to plotters.

Sometimes data can be recovered using relatively simple methods and tools,

but more serious damage, especially if parts of the files are unrecoverable, may require expert intervention.

Data carving is the recovery of parts of damaged files by understanding the structure of those files.
Data engraving refers to the process of extracting data from a larger set of data.

The Data engraving is said to re-assemble files from multiple raw pieces of data at a time when no file system metadata is available.

Another problem that can drive the user to the error display stage is the damage to the partition table. Fortunately, this problem can be solved by software correction.

If you can successfully repair the partition table, you can easily recover lost files.

Otherwise, depending on the level of damage, you can still recover enough data from the partition table and recover the file.

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Even if the files you are restoring are damaged, you will most likely be able to recover a significant portion of them using data recovery software.

In this case, as long as the software is able to find the file, it will attempt to recover it. Although you may not be able to use the recovered data,

But there is always the opportunity to recover part of the file, which can save time trying to recreate it.

Overwritten data

After the data is physically overwritten on a hard drive, it is generally assumed that in such cases the previous data will no longer be recoverable.

Peter Gutmann, a computer scientist, presented an article that could retrieve transcribed data using magnetic force-based microscopes.

this scientist presented several articles with similar titles. In order to protect against this type of data recovery, Peter Gutman and Colin Plum have a method of disk scrubbing

Known as the Gutman Method, they were designed to be used by several disk cleaning software packages.

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The first and foremost criticism of Gutman’s cached data recovery article is the uncertainty of the amount of cached data recoverable.

Although Gutman’s theory may be correct at first glance, there is no practical evidence that the overwritten data can be retrieved, and overwritten data cannot be retrieved according to various studies.

The overwriting of data in solid state drives (SSDs) is quite different from hard disk drives (HDDs), which at least makes it easier to recover some data.

Most solid-state drives use flash memory to store data on pages and blocks.

These pages and blocks are used by the Logical Block Address (LBA) managed by the Flash Transfer Layer (FTL).

When the flash transfer layer modifies a sector, it writes new data elsewhere and updates the map so that new data appears in the target logical block addresses.

As a result, pre-modified on-site data can be retrieved using data recovery software.

Formatted, erased and lost data

Sometimes data on physical drives such as internal and external hard drives, pen drives, etc. are lost or deleted by pressing the Delete key.

Sometimes you may see important data being deleted due to disasters such as viral attacks, accidental deletions or accidental pressing of Shift + Delete keys.

In such cases, it is easy to use data recovery software to recover or recover files and data.

Damage or formatting of the file system

Similar to deleting a file, formatting the file system also damages all previous file information and disk structure, except that the amount of deleted data depends on the system format.

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For example, FAT formatting will destroy a lot of data and overwrite that part with zero.

This will significantly reduce the likelihood of data recovery. Some file systems, such as NTFS, have a high overall recovery probability of being overwritten with the same file system.

But other file systems in the same state will have less chance of recovery. For example, writing an XFS file system on a FAT makes it more likely to recover FAT files.

In the case of file system damage, the number of recoverable files depends on the extent of the damage and the availability of information allocated to the recovery software.

If enough data is provided to the data recovery software to repair the file system and the preceding files are precisely located, a significant amount of it can be recovered.

Bad logical sectors

In the list of hard disk logical failures, the bad logical sector is one of the most common cases where data files cannot be retrieved from a particular sector of media drives.

To solve this problem, software is used to modify the logical sectors of the media storage drive.

If the solution is not enough, the hardware section containing the bad logical sectors should be replaced.

Data Recovery Techniques

Recovering information from hardware that has been physically damaged involves various techniques. Some injuries can be repaired by replacing part of the hard drive.

Although this can make a hard drive usable, there may still be logical damage.

There is a proprietary disk imaging method that is used to retrieve any readable bit from the disk surface.

Once this image is obtained and stored in a trusted location, it can be safely analyzed and analyzed for logical damage analysis.

. In this case, it will be possible to upgrade and restore the original file system further.

Hardware repairs

One of the most common misconceptions about hard drive hardware and data recovery is that a damaged PCB can be easily replaced with a similar PCB from a healthy drive during the recovery process.

But this may be true only for the rare cases of hard drives that were manufactured before year 3. On new hard drives this is impossible.

Advanced boards of electronic storage drives, typically with dedicated drive data

(Usually including a map of bad sectors and scaling parameters) and other information needed to properly access data on the drive.

Replaced boards often require this information to effectively recover all data. The switched board may need to be rescheduled.

Some hard disk drive companies, such as Sigit, store this information in a sequential EEPROM that can be deleted and transferred to the replacement board.

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Each hard disk drive has a system area or service area that acts as the transmitter board.

This part of the drive that is not directly accessible to end users,
They usually have drive formats and compatibility data that help drive performance in the normal range of parameters.

One of the tasks of the system area is to record faulty sectors within the drive. The section basically tells the drive where the drive can write data or refrain from writing data.

Sector lists are also stored on different chips connected to the PCB and are unique to each hard drive.

If the data in the PCB does not match the data stored on the plotter

the storage drive will not be able to calibrate and adjust properly.

However, due to the lack of data matching the data stored on the PCB, hard disks will often only click.

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