Data Recovery: Engineers vs. Software, Part 1

Good data recovery software should be part of everyone’s toolkit but they can’t get a storage administrator out of every scrape. In part 1, Sean Barry of OnTrack Data Recovery examines the benefits and pitfalls of built-in recovery apps and off-the-shelf utilities.

By Sean Barry

What is Data Recovery?

Data Recovery is a phrase that gets bandied about freely in glossy computer magazines and in airport advertising. Type ‘data recovery’ into any search engine and you’ll discover that the Internet is saturated with links of rescuing data.

This begs the question; what is data recovery?

Merriam-Webster defines recovery as the “act or process of getting something back.” In the computer environment, file data can represent all sorts of information types; picture, music, multimedia, spreadsheets, and document files.

Data recovery, then, is the reclamation of lost or missing original data. Computer data is fluid; it changes constantly. For example, this article went through six drafts, while the content is generally the same during drafts, there is a significant difference between draft 1 and 6. If this document file were lost before publication, the most recent original version—not a copy from the last backup—would be required.

What are your options when data loss happens? This article concentrates on what data recovery is and reveals some misconceptions associated with data recovery. Additionally, the discussion will focus on the pros and cons of data recovery software.

Data Loss - Point of Failure

Data recovery is required when access to file data fails. This point of failure can be caused by physical or electronic problems with the storage device. When there is a physical problem with the storage device, focus is placed on getting the device operational so that the data can be read and extracted.

If there is nothing wrong with the storage device but the files are inaccessible, then next point of failure can be caused by errors within the file system. All storage devices need a system of organizing and mapping out stored files. When this file system information is corrupted, the data may still physically reside on the device, yet the ‘pointers’ or ‘map’ to the files requires repair to make the connection from file name to the file data.

Data Recovery Utilities – What They Are Not

Let’s focus on the file system repair. Most users with a working knowledge of the operating system they use may be familiar with some of the volume* repair tools that come with the system they have. Here’s a list of operating systems and their volume repair tools:

Microsoft DOS and Windows Scandisk and CHKDSK
UNIX and Linux FSCK
Novell Netware VREPAIR and REBUILD
Apple Mac DISK FIRST AID

These utilities are sometimes referred to as data recovery tools because they fix the file system. It is more accurate to describe these utilities as ‘volume repair’ tools. These tools do not verify the file data; they analyze the file system itself. The goal of these tools is to make sure that the volume is “consistent” or without error.

Because these tools are designed to fix the volume, any file system references, or ‘pointers’ that are incorrect or that conflict with other ‘pointers’, will be rectified. The danger of volume repair tools is the repairs are made to fix the volume—not preserve data; these changes to the file system may sacrifice the data in order to make the volume consistent.

Many users have asked why these utilities would cause such damage. The answer lies in the purpose of these programs. These repair utilities are volume repair tools, not data recovery tools. Most volume repair tools to their credit, however, have some sort of ‘Read-Only’ mode that will allow you view the problems found without committing to fix them. This allows you could make a choice as to whether to allow the utility to fix the errors. If the repair tool reports a long list of errors in read only mode, then an alternative solution should be looked into to preserve the original data.

* A volume is the physical amount of hard disk storage space that has been formatted with a file system. Volumes contain data files.

Page 2: Automated Data Recovery Software

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This article was first published on EnterpriseITPlanet.com.






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