How many disks can fail in RAID 5?

What is RAID 5?

RAID 5 is a modern RAID level meant to simplify the complexities of RAID 6. It supports data stripping with distributed parity, which makes it capable of withstanding a single failed disk at a time. Setting up a RAID 5 is much simpler and costs less than setting up a RAID 6. Data stripping in RAID 5 means new data is stripped and distributed across member disks in the array.

The essence of RAID storage is to buy some time for yourself to recover your data when one of your storage drives fails. RAID 5 can still function perfectly when one drive fails, this is because the RAID will try to read and calculate parity data from the remaining “good” drives. But even at this, you should make plans to replace the failed drive as soon as possible.

Minimum drives for RAID 5: at least three (3) identical disks; the layout can be configured in different ways. RAID 5’s distributed parity eliminates the chances of facing a bottleneck situation due to too much stress on the dedicated parity disk. RAID 5 also offers improved write speeds since the write requests are coming from all connected drives.

Most people who set up RAID 5 do so because they want an edge in data loss scenarios. With RAID 5, you may not need a third-party data recovery software to get back files from a failed drive in the array – by simply reinserting a new “good” drive to replace the failed one, the RAID will rebuild itself and all your data/files will be complete with none missing.

What Happens When One Drive Fails in RAID 5?

When one drive fails in RAID 5, data will be read from the remaining member drives that are still showing “online” on the array. This happens because when a RAID 5 is set up and data starts coming into the array, it strips the data and distributes the parity across all the connected disks.

Hence, in the event of a single drive failure, the RAID will attempt to read that distributed parity information from all “online” disks and find a way to re-construct any “missing” data. However once a disk fails in this RAID, performance is reduced because the system will put more effort into reconstructing the parity data obtained from the online disks to fix the missing data on the failed disk.

Recover RAID 5 Data Loss with One Drive Failure

There are basically two ways to recover lost data in a RAID configuration; the first one does not require any advanced action or settings, but the second one will require you to install a professional RAID data recovery software. It is important to say that the recovery method you’ll be left with depends on the number of drive failures you have in the RAID 5 array.

Method 1: Hot-swap the Failed Drive

First things first, you must understand that this method is subject to one disk failure in your RAID 5; if there is more than one failed drive in your RAID 5 array, this won’t work. So you have to try out the second method. Also, your RAID controller plays a role in determining if a “hot-swap” can rebuild your RAID 5 automatically and no data will be lost.

In this context, “Hot-Swap” means to quickly replace a failed drive in your RAID 5 array without shutting down the system. However, if any interruptions should occur during the hot-swap or automatic rebuilding process by the RAID, you may end up facing a data loss scenario. Strict carefulness is required here:

• Step One: Identify the failed drive in your array and note down the specs and features.
• Step Two: Purchase exactly the same drive from the market and come to replace the old one; open the RAID disk array and remove the failed drive, then reinsert the new drive you just bought.
• Step Three: The RAID controller will initiate an automatic rebuilding of the array using parity information from the other online drives.
• Step Four: Wait for the rebuilding to complete and then start using your RAID 5 again.
• Step Five: If you have any previous data backup (on the failed drive) saved elsewhere, you can recover it to the new drive.

Note: This will only work if you’re facing just one failed drive in the array and if your RAID controller supports automatic rebuilding. You don’t need to make any configurations to the newly added disk, the RAID controller will do that (if there’s a need for such).

Method 2: Use RAID Data Recovery Software by DiskInternals

Sadly, if you noticed that you’ve got two failed drives in your RAID 5 setup, your best bet is to rebuild the array manually. But before you rebuild it manually, you need to recover your files and data from the failed drives, which is only feasible using third-party data recovery software. Interestingly, DiskInternals RAID Recovery is the top choice of many IT professionals.

DiskInternals data recovery software for RAID works on all Windows OS computers, including systems running Windows Server editions. It is a piece of intuitive utility with user-friendly RAID recovery features. Plus, the software supports all RAID types, file systems, and NAS.

It may interest you to know that DiskInternals RAID Recovery can scan and recover data from RAID drives that were partially rebuilt. Here’s how to use DiskInternals for your RAID 5 recovery.

Guide:

• Download and install DiskInternals RAID Recovery on your PC running Windows 7-11 or Windows Server 2003-2019.
• Launch the program and make sure your RAID 5 drives are properly connected and accessible on the PC.
• If you want to run the recovery manually, close the “Wizard,” otherwise, follow the Wizard’s automatic recovery prompts.
• Select the failed drives you want to recover from (one at a time), identify the RAID array type, and proceed to choose a Recovery Mode. It is best to use Full Recovery mode to ensure complete and effective results.
• Once you launch the recovery scan, DiskInternals RAID Recovery will automatically check the status of the RAID array, file system, controller, and disks, before proceeding to attempt the data recovery.
• When the scan runs completes, which may take hours depending on the data size of the disks, you will see all recovered files along with the existing files you have on the drive. The recovered files are marked with a red asterisk for easy identification.

Note: The recovered files will be available as “Read Only.” You can preview most of them to confirm they are the ones you want to recover. To save them back, you have to upgrade to the DiskInternals RAID Recovery PRO version.

Need to Verify Your RAID Setup?

Use our RAID Calculator to quickly understand your array configuration and find the best recovery approach. It’s simple, accurate, and can save you valuable time before starting data recovery.