Put very simply, Redundant Array of Independent Disks (RAID) is a storage technology which uses multiple hard disks operating as a single unit. From its inception decades ago the technology has developed into many forms most of which have been developed to allow for hard disk failure without data loss.
HOW DOES RAID WORK?
Raid configurations (known as levels) work in different ways with the most common being Raid 0, 1 and 5; there are many Raid levels but for brevity this text will concentrate on the most common.
> Raid 0 is designed primarily for speed, data is striped over 2 or more disks with no redundancy meaning Raid 0 isn't a Raid in the true sense as the Raid will not operate if any disks are removed from the set.
> Raid 1 is designed with 2 hard disks which have the data mirrored against each other, if either of the disks fail the data can still be accessed.
> Raid 5 is made up of 3 or more disks which use data striping with data parity, this allows for disk failure on any 1 disk out of the set without data loss.
WHY HAS MY RAID FAILED IF IT IS SUPPOSED TO STOP DATA LOSS?
> Raid 0 - If a problem occurs with any of the disks the Raid will fail.
> Raid 1 - If both disks fail the data will not be accessible.
> Raid 5 - If 2 or more of the disks fail the Raid with not operate normally.
CAN I DO ANYTHING?
Without specialist equipment and experience no. Having an understanding of how Raid technology works and being technically competent is simply not enough for dealing with a failed Raid system. The process of recovering data from a single hard disk is on its own a mine field; this is exacerbated with Raid given it's advanced methodologies.
SOMEONE TOLD ME THERE IS A PROGRAM THAT CAN HELP / THE RAID MANUFACTURER TOLD ME TO UPDATE THE FIRMWARE.
Not true unfortunately. There is no way of downloading an application that will make everything better; even technical support departments from Raid manufacturers can make a failed Raid worse as in some instances when they give advise such as update the firmware. Updating the firmware formats the partition, severing access to the data and in some worst case scenarios destroying the data.
HOW DO YOU GET MY DATA BACK?
Each case is unique, the first thing to do is address the issue(s) with each disk with the aim of getting a full clone of each disk. This in itself is problematic due to the vast number of ways in which hard disks can fail. At this point it is essential to determine the parameters of the Raid such as disk order, stripe size and parity rotation for Raid 5.
When the parameters have been determined the Raid is rebuilt virtually to provide access to the data; at this point during a normal recovery it is possible to see partition information as well as directory structure, file information and associated meta data. The data is then copied to secure storage and sent back on new media.6 Years, 6 Months, 2 Weeks, 6 Days, 13 Hours, 29 Minutes ago.