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How to Recover RAID 5 Data – The Gillware Method

How to Recover RAID 5 Data

RAID 5 is a popular RAID level for data storage, seeing use in servers for businesses of all shapes and sizes. While RAID 5 is resilient and features redundant data to protect itself in case of a hard drive failure, it is not immune to failure, and a RAID 5 failure can be devastating. Loss of data, loss of revenue, and loss of customer confidence can set you back days, weeks, or even months. The consequences of RAID 5 data loss can wreak havoc on your business—if you don’t start looking for data recovery solutions on the double.


 

The RAID data recovery experts here at Gillware know how to recover RAID 5 data better than anyone else.

Gillware's data recovery lab collects some of the most brilliant RAID recovery engineers in the world under one roof.


Gillware Data Recovery has a simple, step-by-step method to recover RAID 5 data after a server crash. With our nine-step process, our RAID recovery experts have saved thousands of clients from their failed RAID 5 servers over our past decade-plus of data recovery work. Our data recovery process is 100% financially risk-free, with free inbound shipping and free evaluations. We don’t charge our clients for our work until we successfully meet their data recovery goals.

RAID 5 Data Recovery: A How-To Guide to RAID 5 Reconstruction Using the Gillware Method

 

Gillware has a nine-step process to recover data from crashed RAID 5 servers and NAS devices:

  • Step One: Make write-protected (read-only) disk clones of each of the healthy hard drives in the array.
  • Step Two: Diagnose any broken drives, make the necessary repairs, and create as complete disk images of them as possible.
  • Step Three: By analyzing the RAID metadata on each drive, determine which drive (if any) is stale and should be excluded.
  • Step Four: Use the metadata on each hard drive to determine the RAID array’s geometry, drive order, parity, rotation, stripe size, and RAID algorithm.
  • Step Five: Emulate the physical RAID 5 array and find the logical units on the array.
  • Step Six: Find the filesystem geometry within these logical units.
  • Step Seven: Extract and test sample files to make sure the array has been correctly reassembled.
  • Step Eight: If necessary, run a raw scan of the RAID 5 array to pick up any files which may have disappeared due to filesystem damage.
  • Step Nine: Extract all available data from the RAID 5 array.

Read on to learn what goes on in each step in further detail:


Step One: Make write-protected (read-only) disk clones of each of the healthy hard drives in the array.

Gillware’s first step to recover RAID 5 data is to take each of the healthy hard drives in the failed array and create write-protected disk images of them. Our disk image is a 100% identical copy of the original drive, down to the last bit. By using write-blocking tools, we ensure that we’ve created the most exact replica possible and can’t alter any of the data (on either the original drive or its clone).

Because RAID 5 has single-drive fault tolerance, a RAID 5 array won’t crash, even after one hard drive has failed. However, if a second hard drive fails, the RAID array and your data become inaccessible.

Step Two: Diagnose any broken drives, make the necessary repairs, and create as complete disk images of them as possible.

The failed RAID 5 arrays we receive in our lab tend to have two or more failed hard drives. We need to image the broken hard drives, too. But before we can do that, we must fix them first. We make the necessary repairs in our Madison, Wisconsin-based data recovery lab, which features ISO 5 Class 100 cleanroom workstations and an ample library of replacement hard drive parts.

After repairing the drives, we make disk images of them as well as the healthy drives. Sometimes, if a hard drive’s hard disk platters have become scratched or scored, a 100% complete disk image isn’t possible. This is due to the destruction of physical sectors on the disks, which we cannot reverse.

Step Three: By analyzing the RAID metadata on each drive, determine which drive (if any) is stale and should be excluded.

Every hard drive in a RAID array has metadata placed on it to help determine its role in the array. The metadata, among other things, can tell us the last time data was written to a given drive in the array, helping us determine which failed hard drive is stale. Out of two failed hard drives in a RAID 5 array, we only need one to “fill in” the holes in the array. We avoid using the stale drive to fill in these holes whenever possible. But in some situations, in order to recover RAID 5 data, our engineers have to rebuild the RAID 5 array with the stale drive and salvage the usable data from the array.


RAID 5 uses special parity functions to reconstruct lost data if one drive fails, but cannot handle two drive failures. After one hard drive fails, the rest of the array functions normally. But as time passes, the data trapped on the failed drive becomes increasingly out-of-date. Sometimes, two or more hard drives fail almost instantaneously. But in most RAID 5 recovery cases, one of the failed drives has become stale.

Step Four: Use the metadata on each hard drive to determine the RAID array’s geometry, drive order, parity, rotation, stripe size, and RAID algorithm.

RAID 5 arrays use parity calculations to provide fault tolerance if one hard drive fails. The parity data created by the array spreads out in a particular pattern throughout the drives. In order to reconstruct the failed array, we must understand exactly how this parity data has been spread out. Using the metadata on each drive, our RAID recovery engineers can determine how the array has distributed this data across the drives.

Step Five: Emulate the physical RAID 5 array and find the logical units on the array.

To rebuild the array, our RAID recovery technicians write customized emulation software to string the disk images together. We can then identify how the array’s storage space has been carved up into logical units. Small RAID 5 arrays will often have one logical unit spanning their entire capacity. Larger storage area networks may carve up their storage space into multiple units.

Step Six: Find the filesystem geometry within these logical units.

Many of the RAID 5 arrays we see here at Gillware have suffered physical damage. But we also see RAID arrays that have suffered logical damage as well (and occasionally, both). The filesystem comprises the backbone of your RAID’s logical structure, acting as a roadmap to point you to the locations of your files.

Step Seven: Extract and test sample files to make sure the array has been correctly reassembled.

RAID 5 arrays break all of the data written to them into stripes, distributed across the array’s hard drives. If we don't put the stripes together in the right order, useful data turns into a Picasso painting (only with less value to the artistic world). By testing large files—large enough to have chunks on every drive in the array—our engineers can make we've placed the disk images in the proper order. Since this testing method works best with bitmap image files, our engineers call it “the bitmap method”.

Step Eight: If necessary, run a raw scan of the RAID 5 array to pick up any files which may have disappeared due to filesystem damage.

Logical damage to a RAID 5 array can cause damage to the filesystem. This can erase the signposts pointing to some files and make them appear to have vanished. Using advanced data recovery tools of our own design, we can scan through the reconstructed RAID 5 array to pick up any files that the directory structure may have made “homeless”.

Step Nine: Extract all available data from the RAID 5 array.

Our work to recover RAID 5 data ends with the failed RAID 5 array properly reassembled. Finally, our RAID recovery engineers pull off all available data from the array and place it on a healthy external hard drive to return to the client. Our engineers make sure that the client’s most important data is as functional as possible. If necessary, we show our client a list of recovered files to make sure we have successfully met their goals.

Gillware: The Best Choice for RAID 5 Data Recovery

When your RAID crashes, your first instinct will be to look for data recovery software.

And if you find free data recovery software, whether for Mac or for Windows or for Linux, all the better.

But RAID recovery software isn't likely to help in really severe cases.

These products simply aren't as strong as what data recovery professionals use, especially ones you can download for free. Maybe you can recover deleted files from a healthy RAID or salvage data when two of your drives have just had a little hiccup and are otherwise healthy.

But any existing software you can find, even RAID recovery software that's really powerful, won't provide you with the skill and expertise to recover data from severely failed NAS devices and servers.

Any data recovery program or utility you get through a free download will let you work through all of these steps on your own. If the situation is truly dire, DIY data recovery utilities could even make it worse!

Keep your array safe and give Gillware's client advisors a call.

Gillware's professional data recovery lab in Madison, Wisconsin is one of the top data recovery labs in the world.

Gillware offers:

  • Free inbound shipping to our lab
  • Free evaluations
  • No upfront charges
  • "No Data, No Charge" guarantee
  • Emergency service options with 1-4 day turnaround times
  • A professional, ISO 5 Class 100 data recovery lab and SOC 2 Type II compliant facilities

Data loss, especially when it's from a crashed RAID 5 server that's ground your business to a halt, is never an easy or painless thing to go through, but we strive to alleviate as much of the pain as possible.

Will Ascenzo
Will Ascenzo
Will is the lead blogger, copywriter, and copy editor for Gillware Data Recovery and Forensics, and a staunch advocate against the abuse of innocent semicolons.
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