Summary: RAID stands for redundant array of inexpensive/independent disks, and it is a data storage visualization technology in which multiple physical disk drive components are combined into one logical unit to bring about and reap the benefits of data redundancy or performance improvement or both. Depending upon the required level of redundancy and performance, data is distributed across the drives in one of the several ways known as RAID levels. Each RAID level provides a different balance of performance, availability, capacity, and reliability. Here in this blog, Explained about the RAID 5, why it gets fail, how can you make RAID 5 data recovery in an easy way.
Sneak Peek into RAID 5
RAID levels are generally assigned alphanumeric names such as RAID 0, RAID 1 and so on with the number representing the level number. A higher numbered RAID array indicates better protection against unrecoverable sector read errors and whole physical drive failures. Therefore, RAID 5, which is our main focus in this article, is a fairly robust level of RAID arrays characterized by a presence of minimum 3 disks and block-level striping with distributed parity. This RAID level offer advantages such as good performance, higher redundancy, and cost-effectiveness to databases that are heavily read oriented (write operations are slower in RAID 5.
RAID 5 failure – why it happens?
The main power of RAID 5 is derived from the fact that here, parity information is distributed among the drives such that even if one (and only one) of the drives fails but the others are working, everything will continue to operate successfully with no data loss.
However, serious disaster can strike during array rebuilding. It is an activity that takes much time and quite often results in drive failure. Moreover, rebuilding an array requires reading data from all disks opening a chance for a second drive failure and thus, the loss of an entire array.
Another scenario for RAID 5 to fail is trying to force the array back online with one failed drive. Though the description of RAID 5 says that it can operate with one failed disk and most RAID 5 controllers, have a “force online” function, if the wrong drive is pushed back online first, it will corrupt the entire array within no time.
So to summarize, RAID 5 can fail due to the following primary reasons:
- Failure of two drives at once.
- Forcing RAID 5 array back online with a failed drive.
Other more common reasons include:
- Malfunctioned controller
- Missing RAID partition
- Incorrect RAID volume configuration
Additionally, one could wonder why even one of the RAID drives would fail in the first place. Well, since each RAID drive is just another hard drive, the reasons behind its failure are the same as that for any other HDD:
- Sudden power surge
- Virus / Malware infection and so on.
So if you’re organization relies on RAID 5 and the drives fail causing data inaccessibility, you could end up incurring huge losses. Hence, knowing how to perform RAID 5 data recovery is of utmost importance.
Recovering data from failed RAID 5 array
In most cases of RAID 5 failure, all data is recoverable if you act swiftly and take care of a few things. The following fixes can help:
- As a first step shut the PC down. That’s right, just stop working on it and shut it down. The reason behind it is that while 2 of the RAID disks have already gone (leading to the failure), your RAID controller might still be working and might perform writes on the other drives causing them to fail too. So until you know better, just shut down the PC.
- Arrange the necessary hardware and software for performing a complete RAID recovery in one shot without any interruptions. You’ll need:
- A spare PC or external storage (preferably NAS) with enough space as the total size of the original RAID disks.
- A UPS that can power your PC, the spare PC or NAS, a router and an HDD dock if required. No power interruptions should halt the recovery.
- An external HDD dock or another spare PC where your failed RAID disks will be attached to a bootable Windows OS for recovery.
- Trustworthy RAID 5 data recovery software like Stellar Data Recovery Technician.
- Disassemble all the drives from the RAID array, and one by one check their physical integrity by running your drive vendor’s checking utilities. Here you need only to identify the failed drives and NOT attempt to repair them.
- Note down the numbers/names and other parameters of the disks that have failed.
- Now you need to run RAID recovery on the failed disks. To know the steps for that, proceed to the next section.
RAID 5 data recovery using Stellar software
Download, install and launch RAID data recovery (Stellar Data Recovery Technician). Then follow the below-mentioned steps:
- On the main screen, click on RAID Recovery.
- Select the RAID 5 tab and then select the hard drives to reconstruct RAID from the names/numbers of the failed disks you had noted earlier. Also provide other necessary parameters required by the software such as disk order, RAID Start Sector, Stripe/Block Size, Parity Order/Rotation, and Parity Repetition/Delay. If you’re not aware of any parameters, mention ‘Don’t know’ and check mark all possible options given in the drop-down menu.
- Click on the ‘BUILD RAID’ button to see the probable RAID construction. Select the appropriate RAID construction and click on the ‘Show Volume List’ button to go to the data recovery window.
- The volumes in the chosen RAID construction get listed, which can be selected to perform various data recovery operations. Here if you want to select another RAID construction from the previous list, click the ‘Load Constructed RAID’ button. You can also create an altogether new RAID construction by clicking the ‘Reconstruct RAID’ button.
We have come across manual and as well as an alternative method for RAID 5 data recovery, Losing an entire RAID 5 array could be disastrous. Don’t let yourself come to that stage. As a thumb rule, always, ALWAYS backup your RAID arrays. Plus, keep reliable software like Stellar Data Recovery Technician handy for catastrophes.