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Backup software error

Whilst backing up data to tape is a vital part of any IT data security procedure, checking that the backups have worked is sometimes overlooked, yet if there has been a problem with the backup there is a chance that when a restore is required following a server crash or a problem with a disk or RAID, it might not be possible to restore the files that are needed. So why will a restore fail? Setting aside the physical problems relating to damaged tape media or backups recorded by failing tape drives, there are still plenty of things that can go wrong. To balance this it must be pointed out that things do not often go wrong, it is just that when they do it will be just at the time when everything is relying on a successful restoration of data.

Human failure

Nearly every type of failure that leads to the need for a data recovery service is in reality a human error, to some extent anyhow. Data security is all about balancing risk against effort and cost so a home user will not employ robotic tape libraries and keep the household accounts and video collection in an underground vault because it cannot be justified, but a corporation will (well should) invest resources in ensuring that duplicate copies of critical data are available in the event of anything from accidental deletion to the destruction of a building. Setting this aside, there are few of us who do not use some mechanism for backing up and securing data, the problem is most often that we believe that the process has been successful rather than checking it. Simple operations such as checking log files from backup operations are often overlooked. Test restoration of data is not done in many environments as the time and equipment requirements are considered too onerous. Reliance on a single backup copy of vital data is often at the heart of a data security strategem, and when we rely on one thing only, it is bound to go wrong.

So what types of things can fail?

The process of data backup to tape involves the reading of files from a file system, the transfer of data via memory, the encapsulation if the data within whatever housekeeping structure the backup software uses and the eventual committal of the data to the tape.

File access errors

If a file cannot be read from the file system the backup software cannot transfer it to a tape, whilst this sounds obvious experience shows us that read failures or errors are often overlooked. It would be a denial of the laws of physics to claim that a file that never made it to the tape could be recovered from it, but what can happen is that the incidence of a file where the reading process terminated prematurely can prevent access to other files further into the backup. So, access to a set of important spreadsheets can be prevented by the incidence of a failed file earlier within the backed up data. A data recovery service can help with this.

Backup Set Termination

Most backup applications use some form of catalog to hold information regarding the data that is stored, and if this information is or becomes unavailable a re-cataloguing operation is required to re-create it. With some applications and failure to completely read from the set of backup tapes can prevent the cataloguing operation completing and without this information no data can be restored. A professional tape data recovery service is not reliant upon the originating backup software and will work directly on the data recovering all of the data that is present regardless of the completion status of the backup.

Other problems

Other problems can involve the corruption of data as a result of file system problems or memory conflicts within a system. Data that is corrupted cannot be magically repaired and restored to its original condition but with some types of data there is much that can be done. Page based databases, for example MSSQL and Exchange can be salvaged and worked upon to recover the information that still exists in an accessible form, even when there are significant problems.

The Data Recovery Process

The data recovery process begins with the securing of all available data from a tape or backup set before any attempts to access files are made. The data recovery specialist must then examine the data at the lowest level to determine what has actually gone wrong, simply resorting to trial and error is not an option. Only through a thorough inspection of the base data can the true cause the the problem be identified and the appropriate restorative action be taken. Altirium's tape data recovery specialists have experience spreading over three decades and the knowledge required to recover the data from even the most complex backup formats

Last Updated (Thursday, 11 June 2009 08:44)

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