Methods to Recover Data from a RAID 6 Array with Multiple Disk Failure

                      Methods to Recover Data from a RAID 6 Array with Multiple Disk Failure

Summary: A RAID 6 array is a type of RAID setup used when enhanced data security is required. However, when a RAID 6 array fails with multiple disk failure, there is a risk of data loss. This guide will help you recover data from a RAID 6 array when one or more disks fail by hot-swapping the failed drives and rebuilding the RAID array.  

For enterprises or home users, data is a critical asset. From confidential files to documents and more, we use various storage media to keep our data safe. A RAID 6 setup is one such data storage solution that provides data security and a centralized location for storing data.

However, as a RAID setup consists of HDDs or SSDs, it is very much prone to data loss. Unlike regular data storage devices, a RAID 6 setup uses dual parity to recover data from a failed RAID 6 array.

Let’s dive further to understand more about RAID 6 and how data recovery is performed from a failed RAID 6 setup.

How Does a RAID 6 Array Work?

RAID 6 is a type of RAID setup comprising a minimum of 4 HDDs or SSDs configured in a striped-block configuration for storing data and parity distributed across the drives. RAID 6 arrays work on the Reed-Solomon error correction codes, which are known for automatically correcting data errors.

While RAID arrays are generally known for enhanced performance, the same is not the case with RAID 6. This is due to its complex checksum algorithms and dual parity, which increases the RAID rebuild time, leading to mediocre performance. However, despite its slow performance, RAID 6 has double parity, which results in increased data availability and disk fault tolerance.

Sometimes, a RAID 6 setup also has multiple reserve drives, which are not used in regular functioning and storage. These are kept empty and are used as hot-spares for hot-swapping when an active storage drive fails.

What Happens When a Disk Fails in a RAID 6 Array?

As RAID setups are susceptible to failure, a big question arises: how many disks can fail in a RAID 6 array? The answer to this question is quite straightforward – a RAID 6 array has a fault tolerance of 2 disk drives. If three or more drives fail, the RAID setup completely fails, and the data stored on it is lost forever.

When a RAID 6 array fails, its functionality depends upon the number of failed drives. If there are one or two disk failure, the disk array status changes to Degraded while remaining functional. Data will become temporarily inaccessible but can be recovered after rebuilding the RAID 6 setup.

However, if a RAID setup has multiple disks-failure, i.e., a three-disk failure or more, the array is marked as Failed and the data becomes impossible to recover.

Reasons behind Data Loss in a Failed RAID 6 Array

While a RAID 6 offers increased reliability, data availability, and double parity, unexpected data loss happens. Here are some reasons why data gets lost from a RAID 6 array –

• Failed RAID array
• RAID Controller failure
• Human error
• Absence of RAID partition
• Drive failure
• Disk read/write error
• URE error
• DDoS attack
• Abrupt shutdown
• Power surge/loss

How to Recover Lost Data from a failed RAID 6?

RAID 6 works on the Reed-Solomon codes. If a portion of data stored on an active drive gets damaged or lost, the array controller automatically recalculates and recovers it using complex checksums and parity.

Performing RAID 6 recovery isn’t as simple as it seems. However, it is not impossible either. As a RAID array is a collection of HDDs/SSDs working together as a single storage drive, recovering lost data from a failed RAID array depends upon the number of failed disks in an array.

Simply put, there are 2 cases of disk failure in a RAID 6 array – Single disk failure and multiple disk failure. Let’s talk about these in detail.

Case 1 – RAID 6 with Single Disk Failure

This is the case where a single active disk or drive fails in a RAID 6 array. This is the simplest case of RAID 6 failure as it only requires a simple hot swapping of the failed disk with a hot-spare one. Once the spare disk is hot-swapped, the RAID controller will automatically start rebuilding the RAID array.

However, if a hot-spare disk is not available, the RAID rebuild process can be initiated manually after replacing the failed disk with a functional disk.

Case 2 – RAID 6 with Multiple Disk Failure

In case of a failed RAID 6 array with multiple disk failure, there are two scenarios to look for –

• If two disks have failed in a RAID 6 array, you can use hot-spare disks connected to the RAID to perform hot swapping. Once this is done, the controller will automatically rebuild the failed RAID 6 array and use parities to recreate the lost data. Follow this guide to rebuild the lost data after hot-swapping the drives.
• As RAID 6 has a failure tolerance of 2 disks, a RAID 6 array with 3 disk failure or more will lead to a complete RAID 6 failure. The status of the array will change to Failed, thereby rendering the data present on the drives inaccessible. In such a scenario, failed drives must be replaced with new ones to recreate the disk array and the file system, followed by restoring data from a backup media.

Expert Solution

While rebuilding a failed RAID 6 array is a great way to recover lost data from a failed RAID array. However, improperly swapping the drives or incorrect rebuild can lead to RAID 6 array becoming inaccessible. Controller failure can also lead to data loss from a RAID 6 setup. In such a situation, you can use a RAID recovery software like Raminfotech Data Recovery Technician.

Using this software helps you perform RAID 6 data recovery in a streamlined manner by first rebuilding the RAID 6 and then scanning the volumes for lost data. Follow the steps mentioned here to perform RAID 6 recovery –

• Purchase and Install Raminfotech Data Recovery Technician from its official store.
• Launch it.
• On its Home Screen, select the type of data you want to recover. By default, All Data is selected. Click on Next to proceed.
• A new ‘RAID Reconstruction’ window will appear. Follow the steps in the given order:
• Select the RAID 6 tab.
• In the Select Hard Drives to Reconstruct RAID section, select the missing Hard drives and click on ‘>’ to add them under the Move hard drives up/down for disk order section. You can remove any hard drive at this stage by clicking on the ‘<’ key.
• In the Move hard drives up/down for disk order section, place the drives in order by using the UP and DOWN buttons present there.

• Then, navigate to the Select RAID Parameters section and choose various parameters using their respective drop-down menus.