How can I recover data from a RAID set with redundancy?
In order to maintain high availability of critical information and increase its safety, the majority of users prefer employing RAID configurations that provide fault tolerance. Such disk setups remain functional after the failure of a single or even several components, making it possible to perform a replacement without data loss. Yet, unfortunately, even redundant configurations are unable to preserve the data in case of software crashes, accidental formatting or deletion and other logical mishaps.
Redundancy in RAID may be achieved through parity or mirroring. The applied method of protection determines the bare minimum of intact disks that will suffice for data recovery:
Two identical copies of data in RAID 1 allows recovering data without one member disk;
Data is split into blocks of a certain size, then a mathematical function is calculated for these blocks and its result is written onto a single disk or distributed between the constituents. Single parity, like in RAID 3, RAID 4, RAID 5 and RAID 7, allows the array to survive the failure of one drive, while double parity, like in RAID 6 compensates for two simultaneous drive failures.
If the number of defective components exceeds the above-given figures, data recovery is only possible after they are repaired. It is not recommended conducting this procedure on one’s own – such a device should be taken to a specialized service center.
Several other factors are also to be considered before entering into the process:
- Writing operations that may be performed by the system, TRIM on solid-state drives or full format will permanently ruin the data deleted or lost from the RAID set;
- Encryption of the RAID volume in most situations won’t impede data recovery as long as the decryption key is available and the critical encryption metadata is intact;
- If you suspect physical issues with any of the disks, it is desirable to create its image and work with the copy instead of the source storage. Don’t try to replace the drive and rebuild the system before the necessary data is extracted.
Recover data from a redundant storage, such as RAID 1, RAID 3, RAID 4, RAID 5, RAID 6, etc.
If the system was affected by some logical failure, the apt data recovery instrument will be able to bring the missing information back. SysDev Laboratories offers UFS Explorer and Recovery Explorer as efficient software solutions that allow processing RAID sets of various levels and types, including standard redundant configurations – RAID 1, RAID 3, RAID 4, RAID 5, RAID 6, etc. Depending on the severity of metadata damage, the software will either detect the initial RAID parameters and reconstruct the storage or give the possibility to assemble the array from its drives or their disk images. Such a RAID set is created as a virtual storage while the data on the real disks is no way modified.
To rescue files from such a RAID unit by means of UFS Explorer RAID Recovery you will need to act according to the following instruction:
Prepare a computer that will be used for data recovery and install the software onto it. It is advisable to take one with an incompatible operating system to avoid configuration updates/overwriting: for example, if you have Linux MD RAID, choose a Windows PC.
Get a storage sufficiently large to locate the recovered data. This may be an internal disk, network folder or any portable storage device.
Attach all the available RAID disks to the computer, paying attention to their correct order. The best shot is to use internal SATA connectors, but it is also possible to utilize USB to SATA adapters or external enclosures, in case of the shortage of ports. Yet, the latter option may affect the speed of the process.
Note: Please refer to the HOW TO section for detailed instructions.
Run UFS Explorer RAID Recovery. If necessary, change the software settings in the respective pane.
Note: If you are going to use disk images instead of the original drives, open the corresponding files with the help of the "Image file or virtual disk" option from the "Open" item in the main menu.
Examine the tree of connected storages on the left of the main window:
5.1 If the disks contain RAID metadata and it wasn’t seriously damaged or overwritten, the array will be assembled automatically and presented in the list. You can recognize it by the special icon, RAID level or the number of disks.
5.2 If the RAID configuration wasn’t reconstructed by the software, RAID can be built manually from its member disks or their images. For this you will need to open RAID Builder by pressing the "Build RAID" button and create a new virtual RAID storage. Depending on the level of your RAID, use one of the following instructions:RAID 1
Add the components of your mirrored set to a new virtual array by selecting the corresponding disk (partition) or using its context menu.
If one of the constituents is not available, include a placeholder that will serve as its substitute.
Choose RAID 1 in the virtual configuration sheet and press "Build this RAID".
Include each member disk (partition) to the new virtual array by double-clicking the respective storage or using its context menu.
If your RAID 3 is degraded, add a placeholder instead of the lacking component.
Adjust the order of the disks: select the needed constituent and relocate it up or down with the help of the arrow-like See to it that the placeholder is positioned correctly.
Choose RAID 3 in the parameters sheet and define the correct size of the stripe.
As soon as you finish, click "Build this RAID".
Insert each drive or partition the RAID set consists of to the new virtual array. For this you may use the respective option in the storage context menu or simply double-click the storage.
For degraded RAID 4 include a placeholder which will indicate the unavailable component.
Establish the accurate order of member disks: select the needed one and move it up or down using the arrow-like Make sure that the placeholder is correctly positioned as well.
Choose RAID 4 in the configuration sheet and define the utilized size of the stripe.
Once you are done, press "Build this RAID".
Add each drive or partition constituting the array to the new virtual RAID. For this you may double-click the storage or use the respective option in the storage context menu.
If your RAID 5 is in the degraded mode, include a placeholder instead of the missing disk.
Set the order of the drives in your RAID 5: select the needed component and move it up or down using the arrow-like buttons. Mind the correct position of the placeholder.
Choose RAID 5 in the configuration sheet and provide correct parameters for your array: the algorithm used for distribution of parity blocks (parity distribution), the size of each data chunk (stripe size), the number of stripes per single parity block (parity delay – if applicable) and the value for shifting the rotation of data/parity (rotation shift value).
Once you have finished, click "Build this RAID".
Add each component of your RAID 6 to the new virtual RAID. For this you may double-click the disk/partition or employ the storage context menu option.
If one or two constituents of your RAID 6 are missing, insert placeholders to indicate them.
Define the correct order of the disks in your RAID 6: you may select and move the components up or down with the help of the arrow-like buttons. Ensure the correct positions of placeholders in the sequence.
Choose RAID 6 in the parameters sheet and provide the correct configuration for your array: the algorithm used for distribution of parity blocks (parity distribution), the size of a data chunk (stripe size), the number of stripes per single parity block (parity delay – if applicable) and the value for shifting the rotation of data/parity (rotation shift value).
After the completion, press "Build this RAID".
Note: If you are not sure concerning the RAID layout, you may make as many RAID reconstruction attempts as you need to guess the right one. To revise the configuration, select “Edit RAID configuration” in the storage context menu. This will open RAID Builder for the array so that you could make the changes and assemble the storage one more time.
Open the volume mounted under the built RAID and explore its content. If the files look intact, that means the RAID parameters were specified correctly and you can scan the storage for lost data with the help of the respective button or the storage context menu option.
Define the preferred parameters of scan or leave the default ones and click "Start scan". Wait for the end of the process.
Check the obtained scan result: you may sort the files by name, date, type, try quick or advanced search and preview images, texts, documents, etc.
Press "Define permanent selection" and select the items you want to save by putting checkmarks next to them.
Click "Save selection" and choose the destination folder for these items in the opened window.
Last update: July 5, 2018