RAID failure service from Datlabs:
Datlabs trained technicians recover failed, damaged and corrupt RAID Systems. We are proficient in rebuilding and recovering all types of multi disk drive computer and server systems i.e. RAID 0, RAID 1, RAID 5, etc : All Operating Systems and File Systems.
Emergency Call: 0207 111 0966.
Below we describe a number of RAID failure case studies which we hope provide advice that you may find helpful, however you can also use our "one to one" technical facility if you need immediate assistance.
RAID Rebuild and Data Restore:
Datlabs provides specialist support and assistance in cases of Hard Disk Drive or Hardware and Software faults resulting in RAID failure, Server failure or NAS failure. We provide professional, friendly, 24x7 technical support in London, Manchester, Leeds, Birmingham, Glasgow, Edinburgh, Belfast, throughout the UK and Europe.
We dont charge the earth !
Implementations of RAID controllers include Mylex, Adaptec, Compaq, HP and IBM. These implementations can rebuild a failed data volume from a hot standby drive or a replacement drive through a hot swap. A rebuild will however fail if two disk volumes fail simultaneously or if part of the native configuration is actually stored on a single failed volume. RAID's can also fail as a result of the following situations and frequently a combination of one or more of them:
- Malfunctioned Controller
- Raid rebuild error or volume reconstruction problem
- Missing RAID partition
- Multiple disk failure in off-line state resulting in loss of RAID volume
- Wrong replacement of good disk element belonging to a working raid volume
- Power Surge
- Data Deletion or reformat
- Virus Attack
- Loss of RAID configuration settings or system registry
- Inadvertent reconfiguration of RAID volume
- Loss of RAID disk access after system or application upgrade
If you have problem with your RAID server, some of the processes listed below may help you to minimize further loss of data or at least increase your chance of successful recovery with the right expert.
RAID drive failure:
Single disk failure where only a number of critical files are required.
This is a most likely situation where it
may be possible for the user to recover stored data fully
and without the need to send the RAID system for recovery
work.
Note: The RAID is still accessible; but without
fault tolerance redundancy any failure of another
disk volume will result in complete RAID server failure.
What to do:
Critical data should be copied out as soon as possible before any rebuild attempt is performed. At this point, the remaining disks making up the RAID volume could be near imminent failure. RAID rebuild process is generally IO intensive and could stress the disks to complete failure. You stand a greater chance to copy out the required data before total failure occurs. Once the critical data is copied out, standard rebuild process could then be carried out.
RAID degraded due to single disk failure:
Disk failure, Raid severely degraded and it is important to save everything including the boot-up operating system and application.
Under these circumstances a re-configuration
of application may not be possible or maybe be too time consuming,
What to do:
The only feasible option is to rebuild the
failed RAID volume. However, it is advisable that you backup
the disk image from all the working disks before a rebuild
is performed. If the rebuild function fails or more
disks fail you still have the backup disk image to fall back
on.
RAID multiple disk drive failure:
Loss of RAID disk volume due to
multiple disks failure, system crashes, power
surge, lost of RAID configuration settings or
other unknown reasons.
In such a case, one may need to seek data recovery assistance.
What to do:
Before proceeding, you may want to consider the following:
- Place a value on your data and consider fully the consequences of losing your business or critical data.
- What will be the true cost of replicating the non accessible data and how long will data entry take.
- Who will be affected yourself, your accountant, your customers, your family etc.
- Select an established Data Recovery service provider with clean room facilities, experienced technical support staff and a well organised customer services operation.
- Before you part with your system hardware, you may want to image all the working disks. It is better to play safe so you will always have a backup set to rework in case the original raid server suffered further corruption of any kinds. A good Data Recovery service provider will offer to undertake this for you.
- Carefully take note of some the following information if it’s applicable.
Stripe block size (normally a multiple factor of 8K) and order of disk elements in which the RAID volume is formed. Such info can normally be found in the RAID BIOS or RAID configuration Manager.
- Description of problems
- Description of user’s attempt
- List of critical data and folders and any special requirements
- Label each disk before taking them out and carefully note the corresponding position.
- Carefully pack your disks or complete system for delivery to your chosen data recovery expert. Both working and damage disks are needed.
If the RAID volume is not longer accessible, do not attempt any rebuild as such act is meaningless and will only complicate the situation. Rebuild only makes sense if you have a degraded and accessible RAID volume.
Here at Datlabs our RAID technicians specialize in the recovery of data stored on failed or inaccessible RAID systems. This recovery work involves rebuilding and restoring individual failed hard disks to a working condition, reconfiguring the data structures, extracting and repairing the data from the operational system.
Bungled RAID 5 rebuild:
Datlabs technicians are frequently engaged by customers who have inadvertently bungled the RAID5 rebuild process. Once a mistake has been made it is not obvious that there is no longer a simple means of rebuilding the RAID and restoring the stored data and operating system.
Config Damage.
The damage occurs if one removes several disks from the RAID5 array, then plugs them back in a different order, and then performs a RAID 5 rebuild. The RAID 5 rebuild, sometimes called a re-synch, re-calculates and rewrites the XOR parity blocks of the array. A rebuild is executed automatically once the drive is removed and re-inserted, or after a power failure.The damage caused can be explained as :-
Original |
1 |
2 |
3 |
P |
4 |
5 |
P |
6 |
7 |
P |
8 |
9 |
P |
10 |
11 |
12 |
With drives swapped |
1 |
2 |
P |
3 |
4 |
5 |
6 |
P |
7 |
P |
9 |
8 |
P |
10 |
12 |
11 |
After the rebuild |
1 |
2 |
P |
X |
4 |
5 |
X |
P |
7 |
X |
9 |
8 |
X |
10 |
12 |
11 |
P is the original parity and X the new parity.
Recovery:
In the above case a software recovery will not be possible.
A manual recovery can be accomplished but only by very experienced and capable technicians.
There is sufficient and relevant data available to rebuild the contents of the array. In the example a recovery requires knowledge of the original and current block sizes and disk order. Datalbs engineers are able to reverse engineer the configuration by iterative means without compromising the stored data.
Further Problems:
At default the RAID controller will instigate the rebuild automatically and in fact will exascerbate the problem. The rebuild in progress will destroy areas of stripped data and by the time the effects are apparent it can be too late for remedial work to be effective.
Restoring Drives in the array:
Without detailed knowledge of the disk drive order it is easy to mistakenly pull out a disk that is not the failed one. When this occurs the failed array will in fact be missing two disks and not just one. A two disk failure situation is beyond the auto recovery capabilities of the RAID 5 config.
In the majority of cases it is possible to bring the array back to life by re-inserting drives in a specific order however it is essential that drives are labelled corresponding to their original port in order to avoid further cock-ups and also identify, remove, and label the faulty drive.
Be aware however that Datlabs recommend that in ALL cases you submit a failed RAID 5 array for data recovery and rebuild . IF YOU MESS UP the order in which you insert the disks you will get an enormous number of zeros added and mixed into the data. This sort of damage is generally fatal to subsequent rebuild and recovery attempts.
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