What is RAID? All you need to know


The RAID system has become a fundamental part for companies that have large volumes of data. Before implementing this system in your company, learn what RAID is, how RAID works and how to implement it.

A RAID is formed by a set of HDDs and SSDs, which need to be configured via the operating system.

They are arrangements or arrays so that the sets work together in a private or public network for notebooks, computers, servers and other types of storage systems.

The main reasons why companies adhere to this technology of grouping disks are: system performance and security in servers and computers.

This means that by choosing a RAID system, we are also improving performance, a gain in performance, in reliability for the whole issue of parity, mirroring, stripping with double parity.

All these aspects bring improvements capable of dramatically increasing productivity and the level of rapid delivery in reading and writing data and files.

The limit to all levels of RAID, is to remember that all hard drives (HDDs) or SSDs have an expiry date.

Devices that are being used for more than 4 years without ceasing, aggressive and unrelenting use, these have an even shorter lifespan.

It can be a RAID hard drive, which are larger and more resistant, but still, because they contain mechanical parts, reading head, magnetism for recording data, will certainly lead to breakage and data loss.

We always recommend to all our customers, partners, to always keep a good backup solution on their servers, RAID, NAS or SAN.

Every time we mention good backup solutions, we mention the 3x2x1 method (3 copies, 2 different media, 1 offline). This method is basic, it is the minimum that every company should have.

What will you find in this article?

What does RAID mean?

The exact translation for RAID (Redundant Array of Independent Disks), is: “Redundant Array of Independent Disks”. This is its exact meaning and below we will explain in a practical way, all this theory.

In practice, is an array with two or more disks or SSDs that form a logical unit of data storage.

This way, instead of having several disks in the folder “My Computer” with the folders named in (Unit C:), (Unit D:), (Unit E:), (Unit F:), and so on, we will have only one folder (Unit C:), for example, which will execute all the work in a unique way.

In this way it is possible to assemble a single array, with several disks or SSDs that will be managed as if they were all a single device.

A RAID system can be implemented and configured via Linux, where the whole RAID volume, all disks together, become just one disk for the operating system.

Recover RAID systems

How to Implement Architectures in a RAID Framework?

To implement a hardware RAID architecture you will only need available hard drives, a RAID controller, a PCI or PCI-e expansion card or a card integrated into the motherboard of your desktop PC in your own home office.

Using an ordinary PC it is possible to do the entire implementation of a RAID architecture.

The hard disks need to be kept in a safe place and even in cases where one of the disks breaks, we have the resource of hot-swapping, which allows us to make the exchange of the broken HD by a new one, while the server continues operating and resources are not ceased until the new disk is restored redundancy or parity of the other disks.

The positive side of implementing a RAID architecture via hardware is that we will always have a performance gain, because regardless of the I/O the controller is able to determine and present only a single disk drive, without overloading the processor (s).

Software RAID Architecture Implementation

If we need a cheaper RAID architecture, without additional costs, the implementation via software is the most suitable.

In this case, because we don’t have a specific controller, all management will be done by the processors in the PC or desktop CPU itself.

For this to be done to obtain performance gains, the processor used needs to have the minimum performance available, so that more resources can be accessed by the system.

The scalability load level of the RAID system is very broad, this means that we can access all its performance, without losses in the middle of the processes.

In this type of project, there is no need to incur high costs in a high value Storage, fortune in Servers, although there are several cases of professionals in companies who work this way.

It’s as if the BIOS received some functions more than a common one, because of the software that is installed and the drivers that are executed via S/O.

Hardware RAID Architecture Implementation

To implement Hardware RAID you need a controller that has its own disks. The hardware implementation has some advantages compared to software, the hardware accumulates cache which speeds up the access to information, besides not requiring the use of the CPU of the server or storage used.

What do the RAID Levels Mean?

They are all technologies that involve the grouping of two or more disks, named as systems in RAID. RAID levels are defined by numerical or alphabetical addition of each of the levels.

This means that setting up arrangements goes far beyond just having a storage unit, but one that can meet the specific demand, the demand for performance and capacity to store the data.

It is not an obligation or something that can not be changed, but what is most indicated to mount an Array, is that all hard drives or SSDs from the same manufacturer, the same model, with the same capacity, so that all resources are used equally.

Today small, medium and large companies use this technology because of the ease of scalability and security.

There are some levels of RAID that are the most used in the market today. Below are some levels used for corporate solutions.


Recover RAID 0

In RAID 0, two or more disks perform read and write tasks simultaneously, delivering the highest performance and freeing up the total capacity of the disks.

When making this arrangement, the system understands that it must use all the available disks by distributing the information between the disks.


Recover RAID 1

RAID 1 or RAID mirroring, was developed with its focus on protecting the environment, because when implementing this system, all data, files and spreadsheets will be recorded in duplicity and simultaneously on the HDs or SSDs.

In an objective way the entire environment will be replicated in both arrangements two disks.


Recover RAID 5

To implement RAID 5, the minimum is three HDDs or SSDs, because there is no mirroring in this, but the parity bits that are created so that data backups are performed.

This is more secure than RAID 0 and 1, because of the configuration parity, is not focused on performance, even though it is quite performant.

For the most demanding, who need high demand of data, the ideal is to mount a configuration on SSD, because it is in flash memory, which makes the whole environment more performant.


Recover RAID 6

In RAID 6 are configured two parities, so this way to create a RAID 6 and this requires at least four hard drives or SSDs to store and perform the reading of recorded data.

This type of RAID is implemented in environments that are very performant and require data security, this is fault tolerant up to 2 hard disks / SSDs in the Arrays.

It works as a junction of high performance and security, while all tasks are executed, to the most critical, it is the best and also the most expensive.


Recover RAID 10

A RAID 10 or 0+1 is the junction of RAID 0 and RAID 1. In this type of RAID the storage can contain numerous disks, and each disk will have another identical disk (mirror) in the same array.

In other words, a RAID 0 is created and for each disk in RAID 0 is created a mirrored disk with the same information. If on the one hand in RAID 10 we have the same performance of RAID 0 and RAID 1 security, it also takes its toll.

The disadvantage of this system is that it will always take half the disks – 50% of available storage – to generate data redundancy, ie if you create an array with 10 disks, you can only use the space equivalent to 5 disks. The other 5 disks will be for the exclusive use of the controller and will be used for generating data redundancy


Recover RAID 50

RAID 50 is a complex combination of RAID 5 and RAID 0. At least 6 disks are required for this type of array. RAID 50 offers the performance of RAID 0 with a higher level of security than RAID 1.

It consists of two or more independent arrays in RAID 5 that are connected in RAID 0. Each array in RAID 5 consists of at least 3 disks and the system will have the equivalent of one redundancy disk space for each array in RAID 5.


Recover RAID 60

Similar to RAID 50, RAID 60 is a combination of RAID 6 and RAID 0. At least 8 disks will be required to create this type of RAID.

This system offers the maximum performance and security among all types of RAID presented here. In this case can fall up to 4 disks at the same time of different sub-arrays and the system will still keep running.

What are the Burdens of a RAID System?

A system that has been implemented on RAID is easily mentioned as a very safe environment, but there are some caveats that need to be addressed and exposed.

The implementation on RAID is safe against system failure, because there are levels of “backups”, because of the mirroring and parity of other configurations.

When we take into account this aspect, we can see that RAID does not actually protect the data, but free the operating system from failures that abruptly stop the entire production line of companies.

The ideal, for all business environments that use Database, Storages, Servers, Virtual Machines or even in Datacenters: to have an excellent Backup solution.

The main data security system is still the good old Backup solution, known as “3x2x1 solution”, where there are three copies of the data in two different types of devices and one of these being offline. This is the most basic of solutions.

The best of worlds would be a backup solution that is updated hourly, every day, for the most critical S/O that cannot stop or have unusual pauses.

For the non-critical environments, ideally at least a daily or weekly worst-case scenario backup should be done.

It is necessary to establish the culture of successful backup strategies , as many fronts are exposed when there is a data loss or data leakage after a hacker attack.

Every time there is a need to engage the services of a technology company for data recovery, it is because protection and security protocols have failed.

Antivirus systems only work as a palliative and not as prevention, as they are sold in marketing strategies in the lists of the best of each year, in the best of the semester and so on.

What Causes Data Loss on a RAID System?

There are several factors that cause a loss of data on a RAID system: human factors, excessive use of the system, lack of maintenance and exchange of disks, problems in the RAID controller.

You can mount a RAID system on a Storage, NAS, SAN Servers in large Data Centers, in all, if there is no RAID controller and technicians who know what they’re doing, will be like a “shot in the dark.

At all levels of RAID, we must emphasize the importance of a well-planned infrastructure, avoiding the false experts who give tips that work for absolutely nothing.

All the necessary care is still little, create a check-up routine, to verify the useful life of the HD or SSD, check via software, how is your health, so that there is no loss of data from RAID HD.

Companies that have a team of technology need to be always evolving, adept at healthy changes, which will bring several benefits and will bring savings in time, money and will add even more value to the company.

Corruption of files on RAID systems are caused by inattention, disconfiguration and even by a malicious person who ends up deleting data permanently.

We need to warn you: the redundancy system it protects you against some disk failures, and is great and easy for system scalability, but this does not exclude the fact that if there is a power failure, errors in operation, system errors.

It is necessary to take into account that if we move to places where we do not dominate, we can suffer damage, perhaps irreversible.

Major Issues Leading to Data Loss on RAID System

Physical Problems

  • Faulty RAID controller
  • Circuit problems
  • Head crash
  • Dirty head
  • Surface damage on disks
  • Faulty blocks – Faulty sectors
  • Natural wear of the media
  • Surface scratches
  • Serious scratches
  • Motor damage
  • Servomechanism problems
  • Defective hard disk bearings
  • Defective hard disk PCB (Printed Circuit Board)
  • Firmware problems
  • Water and/or other liquid damage
  • Undercurrent from the circuit
  • Drop and impact damage

Logical Problems

  • Deleting or corrupting data on partitions
  • Deleting the partition
  • Overwriting information
  • Formatting and subsequent reinstallation of the system
  • Problems with system booting
  • Data desynchronisation from one hard disk to another

Configuration Issues

  • Loss of array data
  • Deletion or modification of RAID controller configuration
  • Array volume deletion or modification
  • Hard drive order loss

Is There a Solution for RAID Data Recovery?

Yes, there are solutions available on the market for data recovery across all RAID levels and models.

Data recovery for RAID is customizable and ideal for all systems. This means that there is the possibility and flexibility to recover all data regardless of the RAID level.

There are isolated cases where data cannot be recovered, due to attempts that instead of solving the problem, have only increased it.

The possibilities of recovery are unitary and there are times, that there is only one attempt, so it is worth emphasizing that the correct choice of company to recover your data is of paramount importance.

The recommendations listed below are based on our many years of experience working with RAID data recovery.

We have the expertise to recover RAID 0, RAID 1, RAID 5, RAID 6, RAID 10, JBOD and others. Before performing any procedure to attempt to recover data from your RAID system, consider these points:

  • Be confident that the procedures being performed will not make the situation worse than it already is.
    In most cases, attempts by technicians who do not specialize in RAID systems further complicate the process of data recovery. Eventually, some of these attempts may make the process of data recovery impossible.
  • Verify that the Backup is up to date. If you do not have a backup, before performing any procedure, the best thing to do is to seek specialized help.
  • Be careful with the Rebuild procedure. Never execute the RAID controller INITIALIZE command. On most controllers, this seemingly harmless command (initialize) will completely reset all existing data on the RAID, making data recovery completely impossible.

Key Information for Recovering a RAID System

When requesting RAID data recovery service, please collect as much information from the RAID as possible. This will make the process easier.

  • Server: Manufacturer, Series and Model
  • RAID Controller Card: Manufacturer, Series and
  • Model
  • RAID Type: RAID 0, RAID 1, RAID 5, RAID 6 or other
  • Hard Drives: Manufacturer, model and capacity
  • Number of physical disks
  • Quantity of logical volumes / logical disks
  • Check if the Operating System and Data were in different Arrays
  • Number of Partitions in each logical volume
  • Operational System: Manufacturer and Version
  • Operating System: Manufacturer and Version
  • Approximate size of each partition
  • How the Data Loss Occurred
  • What was done when the problem was first noticed
  • What procedures were performed in an attempt to repair the problem
  • What happened when attempting to perform the repair procedures
  • How many and which disks in the RAID are at fault
  • Location of all data that needs to be recovered
  • What data (files, folders and partition) needs to be recovered
  • What is the approximate volume of the data

We offer RAID Data Recovery Services from the following manufacturers:

  • Western Digital
  • IBM
  • Iomega
  • D-Link
  • Sinologia
  • Drobo
  • Netgear
  • Promessa
  • LaCie
  • Asustor
  • HP
  • Seagate
  • Búfalo
  • Thecus
  • Intel
  • Areca
  • Adaptec
  • Delock
  • CalDigit

Digital Recovery Company Specializes in RAID System Recovery

Our company specializes in RAID data recovery of all types, sizes and operating systems. Because every hour and minute can count, especially for businesses, we have a special department for RAID data recovery that can operate around the clock. When our customers enter their order, they can engage the 24-hour mode there to ensure the fastest possible recovery.

As a specialist data recovery company, we also regularly accept orders from other data recovery companies and in many cases we can recover data even if a negative prognosis has been made previously. Do you already get a “no”? With us you get a “yes”. Whether it’s a standard hard drive, SSD or SCSI disk, we recover your data on all storage media that can be RAID’d.

We can recover data from the following RAID Levels

  • RAID 0
  • RAID 1
  • RAID 2
  • RAID 4
  • RAID 5
  • RAID 6
  • RAID 7
  • RAID 03
  • RAID 05
  • RAID 10
  • X-RAID
  • RAID 1.5
  • RAID 15
  • RAID 1E
  • RAID 1E0
  • RAID-30
  • RAID-45
  • RAID-50
  • RAID 51
  • RAID 53
  • RAID 55
  • RAID 5E
  • RAID 5EE
  • RAID 5DP
  • RAID-60-Verbund
  • RAID Matrix-RAID
  • RAID S
  • RAID-Z
  • RAID 100

RAID System Data Recovery FAQs

These are the questions we receive most from our clients.

1.My RAID data is inaccessible, what happened?

The most common situations that cause data to become inaccessible and RAID data loss to occur are:

  • Physical damage that occurred on the RAID controller
  • Physical damage to the server’s system board
  • Improper configuration changes to the RAID
  • RAID controller
  • Problems encountered on one or more disks at the same time
  • Problems booting the operating system
  • Loss of disk sequential order
  • Data corruption on GPT or MBR partitions
  • Problems occurring in the Rebuild attempts of one or more disks with
  • problems
  • Improper recreation of both the RAID and the logical volume attached to the
  • array
  • Problems experienced during an increase capacity process
  • RAID was rebuilt or rebooted with a different configuration.

2. Will replacing the RAID controller bring my data back?

The structure of RAID systems is based on three major differentials, which are: Security, performance and increased capacity of dedicated devices for data storage.

The RAID controller is hardware specifically designed for processing information from the volumes and partitions of an array. The controller card has, among others, two main functions: The first of them is to perform all the calculations regarding the data processing and storage of the parity information in the arrays. The second function is to store the configuration data of the arrays created and managed by the controller itself.

A common technique used by the controllers to protect themselves from problems, is to store the data of the managed arrays in reserved areas in the own disks that it uses to create the arrays.

This way, if a controller presents problems, a new controller can be installed and then execute the necessary commands to read the configuration data stored in the disks of the array avoiding data loss. Normally this region of the disk is known as the DACStore.

If in fact the problem is in the controller, because of the protections previously reported, it is very likely that the environment will return to work normally. However, if there is a problem with the information recorded on the disks, the data will remain inaccessible.

3. How long will it take to recover lost data on a RAID?

We understand the disruption and damage a RAID server and storage outage can cause your business. With that in mind, we have created a 24×7 department that is dedicated to assisting customers who have extreme urgency in recovering data from RAID systems.

As soon as disks from a RAID server or storage enter our lab, the advanced diagnostic process begins immediately. The advanced diagnostic process usually takes between 4 to 8 hours. As soon as it is concluded, the customer will be informed about the possibilities of data recovery, the amounts involved, as well as the estimated time for recovery.

The average time for data recovery in servers and RAID storage at Digital Recovery is approximately 36 hours, but in some cases, projects have been solved in less than 12 hours. Depending on the complexity of the problem and the type of solution to be adopted, the time for data recovery may extend for a few days, but at all times a specialist will be in contact with the focal point of the customer, to report in detail on all movements made.

4. Can I recover data when two or more RAID disks fail simultaneously?

Certainly it is possible, as there aare techniques available to reverse this type of scenario, as in most projects, we can safely change the disk status from defunct to online, in order to clone in isolation as soon as possible, the sectors attached to this problematic disk.

5. What is RAID Degraded? How do I know if my RAID is degraded?

A Degraded RAID is when one or more redundancy disks have stopped working. Depending on the type of Array this will imply loss of performance. The surest way to know if the RAID is degraded is by accessing the controller management software. On IBM/Lenovo servers this software is called MegaRAID Storage Manager. Another way to see it is to observe if any orange led is lit on the disks belonging to the array in question.

6. How much does RAID data recovery service cost?

Because of the many variables involved in a RAID data recovery project, it is not possible to know the final value without performing a detailed evaluation. The purpose of this assessment is to determine:

  • Level of complexity and urgency
  • Real possibility of recovery
  • Time to perform the service

To perform an assessment, please contact us through our support channels, which are available 24x7x365.

7. Is it possible to recover data from a RAID remotely?

Yes, in many situations it is possible to recover data from a RAID server or storage remotely. For more information about this recovery modality, please contact us through our support channels, which are available 24x7x365.

8. Is it possible to recover an environment containing LVM?

The Logical Volume Manager (LVM) can be fully recovered as it is an option for managing logical volumes of a hard disk or RAID in Linux/Unix operating environments.

9. My RAID server has stopped working, what should I do?

We have compiled a list based on our many years of experience working with data recovery on RAID systems. Before you perform any procedure to attempt to recover data from your RAID system internally, consider these considerations:

  • Be confident that the procedures being performed will not make the situation worse than it already is.
  • In most cases, attempts by technicians who do not specialize in RAID systems further complicate the data recovery process. Eventually, some of these attempts may make the data recovery process impossible.
  • Verify that the Backup is up to date. If you do not have a backup, before performing any procedure, the best thing to do is to seek specialized help.
  • Be careful with the Rebuild procedure.
  • Never execute the Initialize command. This seemingly harmless command (initialize) will completely reset all data on the RAID, thus making data recovery completely impossible.

10. Why is data lost in RAID 1?

A RAID 1 system is a type of RAID with 100% redundancy. This means that all information on one disk is mirrored or written to another disk. Even when using two disks, only a volume equivalent to one disk will be presented to the operating system.

Whenever the user makes any change to the volume the system responsible for managing RAID 1, (either by software or hardware) will automatically replicate this change on both disks. Once I have 2 mirrored disks and exactly equal what are the possibilities of data loss? Although there is the possibility of simultaneous failure of the two disks, this possibility is very small.

Most data losses on RAID 1 that we receive for recovery come from RAID management failures. See the following situations:

A. After 2 years of continuous use of a RAID 1, one of the disks fails with bad block problems. Because this disk is no longer in normal use, the controller or the array management software will discard any attempt to write or read to this disk. The system will also warn the user of the problem so that he can replace the failed disk quickly. This is exactly where most of the problems occur. Because the system continues working normally, because one of the disks is still 100% functional, the user does not pay attention to the warning and continues using the machine. Six months later, the second disk fails. But this time instead of only presenting failures caused by bad blocks the RAID disk is completely inaccessible. When trying to solve the problem by connecting the disks in another computer or sending to a service center the only disk that will still be accessible is the disk that stopped first (6 months ago), because even presenting bad blocks it may still be possible to access some information, but from 6 months ago.

B. Because much of RAID 1 are mounted on ordinary machines and without the infrastructure (Enclosure and RAID Controller) necessary for RAID systems, they are much more susceptible to failure. Because of this, another problem can happen when one of the disks presents problems in the cable or connection to the motherboard. Although the disks are without any problems, a bad contact in the connection cable of one of them interrupts communication. The Array management system warns the user, but he does not notice. As there is 100% redundancy of the data on another disk, the machine will continue working normally and without performance problems. Some time later, when doing maintenance on the computer, the cables are disconnected and reorganised. In this maintenance there is the risk of reconnecting the HDs in different ports and confusing the system. Once two disks are connected in RAID 1 again the system will identify that they are not equal, because there is enough time that one of them was disconnected from the RAID. At this point the system will update the information from one disk on the other. Since the disks were connected on different ports, the system can simply copy the disk with old information onto the disk with new information.

C. Following the same line as the problems cited above, when one of the disks in RAID 1 fails and the user continues to use the system, there is the possibility of data loss if for some reason the user recreates the array. By doing so, the system will identify that the disks contents are not exactly equal. At this time the system will copy the information from the first disk to the second and data overlapping may occur


11. If I recreate the Array with the old settings will my RAID work again as before?

In some cases yes. Especially when you have an environment with few disks and when you remember exactly the array configurations.

But when you have storage with numerous hard disks, running with multiple volumes, used different RAID configurations and even with Hot Spare disks, even if you have all this documented will not be an easy task to recreate the Array and it will work again.

In the case of Virtualized RAIDs or vRAID even having all the configurations noted the only possibility of returning the Array is by reading the settings contained on disks (DAC Store).

12. How much space is available on a server or storage configured on RAID 5?

Regardless of the number of disks that will be allocated in the array, the system will use the space equivalent to one disk for parity, ie to get the net space, just multiply the capacity of the disks by the number of disks subtracting one.

Example | Considering 5 disks of 3 TB each, totaling 15 TB of raw space.

Subtracting one disk we have a total of 4 disks of 3 TB, ie, 3 TB x 4 = 12 TB

13. Can I recover data when two or more RAID disks fail simultaneously?

Certainly it is possible, as there are techniques available to reverse this type of scenario, as in most projects, we can safely change the disk status from defunct to online, in order to clone in isolation as soon as possible, the sectors attached to this problematic disk.
Isaias Sardinha
Isaias Sardinha
Isaias Sardinha, CEO and founder of Digital Recovery, has been working for more than two decades in the recovery of lost data. He is an expert in disaster recovery and in the development of technologies for data recovery, such as Tracer, a tool capable of recovering data in RAID System, Storage, Virtual Machines, Database and Ransomware.