Saturday, May 23, 2009

The Difficulties of RAID Data Recovery

Originally coined as a cheeky acronym to describe “a Redundant Array of Inexpensive Disks” – a technique which allowed computer users to maximise the reliability of their data storage by using arrays of cheaper and less reliable PC-style disk-drives – “RAID” is now used as a general term for forms of data storage that divide and copy information across multiple hard disks.

The aim of RAID systems is to maximise either the input/output capacity of a storage system or the reliability of its data. However, the complexity of the system means that if data loss occurs, recovering the data is all the more tricky. RAID data recovery is, therefore, a serious business, and experts in data recovery treat information losses in servers or RAID systems as their highest priority.

It is essential to discover whether the storage device in question is accessible to the specialised equipment at the technician’s lab, and so the first step towards RAID data recovery is diagnostic. If this reveals that the equipment is compatible, all available data is copied on to new media to allow the technician to analyse the exact nature of the problem – but if it is not possible to access all of the media using the lab’s equipment, the expert will then test the RAID components for possible physical damage.

RAID data recovery often means replacing any failed or broken components – such as electronics, read/write heads, head assemblies, magnets and drive motors – in a clean environment, which itself requires highly specialised hardware and software tools to build up a raw image of the data. Because of the array of separate disk-drives, technicians need to have specialist skills that allow them to determine both the exact layout of volumes which exist across multiple drives and what repairs to the system’s file structures are necessary to gain access to all the lost data.

As part of the RAID data recovery process, the technicians will usually “destripe” the multiple-drive servers and place them on to the lab’s own media to carry out repairs to the file system. If damage is severe then data needs to be directly extracted from fragments of the destriped image.

The expert programmers utilise a wide range of software tools to analyse, destripe, fix and recover data from raw image drives, which cover nearly all operating systems. Once the RAID data recovery has been achieved, the technicians create file lists and check the validity of the information they have recovered.

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