Data recovery from RAID and servers

Recovering data from a damaged RAID 1 array

What are the characteristics of data recovery from complex disk systems, such as RAID arrays?

The answer is in the question - the complexity of the system in question.

RAID (Redundant Array of Independent Disks) is a method of logically organizing multiple disks so that they form a logical whole, while offering a number of benefits resulting from the use of two or more drives.

The disk array is characterized by the failure rate typical for a single HDD or SSD drive, for which there is also the possibility of damaging the RAID controller at the software or hardware level and the possibility of disrupting data integrity on one or several drives, which may permanently prevent logical reconstruction and data recovery.

Let's look at the two basic types of RAID used most often by home users and small businesses. The most popular array configurations in these applications are RAID0 and RAID1.

RAID0 level array

In the case of RAID0, we divide the data equally among all drives operating in the matrix, thus increasing the available capacity and reading and writing speeds.

This type of array does not provide protection in the event that any disk is damaged and the failure of one of them prevents access to all data.

To recover data from such a matrix, it is necessary to image all disks belonging to the configuration, repairing them if necessary, verifying the order of drives and the stripe size used, and performing logical reconstruction.

RAID1 level array

RAID1 is a so-called mirror array in which each disk belonging to the array contains exactly the same content, and its capacity and writing speed do not increase compared to a single disk.

It allows operation as long as at least one disk that is part of the configuration remains functional, with the reservation that in the event of surface degradation and bad sectors, these errors may be transferred and, as a result, damage data or lead to loss of information integrity.

As long as one drive remains functional, there is usually no problem with accessing the contents and restoring data.

Often, however, the device in which RAID1 is running is not monitored, or warnings and failures are ignored, which ultimately leads to damage to all drives. In such a situation, it is necessary to check which of the drives failed last and from which data should be recovered.

What RAID arrays do we support?

Data recovery from RAID:

RAID 0
RAID 1
RAID 1E
RAID 10
RAID 0+1
RAID 3
RAID 4
RAID 5

RAID 51
RAID 5E
RAID 5EE
RAID 6
RAID 60
JBOD
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What servers do we recover data from?

Manufacturers of storage solutions for which we offer data recovery services:

Dell
Fujitsu
IBM
Qnap
Synology
Buffalo
Asustor

WD Cloud / WD NAS
Netgear
Drobo
Thecus
Terramaster
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SSD RAID Cache

In our opinion, one of the most difficult cases of data recovery from a RAID array with SSD Cache enabled.

The most difficult one because a large part of the logical structure is located on the additional cache, on which TRIM also operates.

The SSD Cache itself is also often configured in some type of array, most often RAID0 or RAID 5, so in the case of a logical rebuild, we must have the configuration and data of the SSD cache and the main array, which we must combine together.

In many cases, if the SSD Cache cannot be reconstructed, the logical structure of the entire array cannot be rebuilt.

Recovering data from a damaged RAID 5 array

Recovering data from a damaged RAID 6 array

RAID array repair and initialization

The most common mistake when a matrix fails is trying to repair it without first securing the data on it.

In the case of each array, if it is possible to access the contents, the data should be immediately copied to other storage media and only after securing them should the reconstruction begin.

If you have lost access to the data on the array, turn off the system and check the extent of damage, preferably by making a binary copy of each disk in the RAID configuration.

In our work, we very often encounter cases of attempts to repair RAID 5 or RAID 6 arrays in which one or two disks are damaged, but during their reconstruction, other disks are degraded or damaged.

If the RAID array is in the Critical, Offline, Degraded, Damage or similar state, its initialization will most often result in data corruption or deletion.