Today, I spoke with a MacBook Pro user regarding lost files on an external hard drive due to a hard drive failure.
He purchased Data Rescue and ran the scan on the external drive to get the .mov movies originally recorded on his home camcorder. After Data Rescue finished scanning the drive, he recovered the files. But the files would not open. This is when he reached out to our support staff, to find out if the movie files could actually be recovered.
I told him that Data Rescue supported .mov file recovery and many Mac users use Data Rescue to recover them. His particular problem seemed to have something else at the heart of the matter. Time for some low-level, technical support guru investigating!
Do You Know You Have A RAID?
After enquiring, I found out that the .mov files were inside of a hard drive enclosure that had two drives in a RAID array. In fact the user had no idea that he had a RAID configuration, and was surprised to learn that was the issue preventing a successful scan. It turns out that he was running a scan on the individual drives separately, when the files were actually spread across the two drives.
I told him that Data Rescue has the capability to recover from the two drives attached to the Mac in a RAID array. Here’s how:
If the RAID array is still intact, you should see it as a single hard drive within the “Select Drive” screen of the software. If so, you will not need to set up special parameters. You can immediately begin scanning the drive.
However, if you are suffering from more severe data loss, and your RAID array is displayed as two separate hard drives, recovery through Data Rescue is still possible, but you will need to re-configure your RAID array through the software itself.
Data Rescue Supports 3 Basic Types Of RAID
Stripe– This is also known as RAID-0. As data is read sequentially from the RAID set, it comes first from the first component drive until a stripe-sized amount has been read, then the next data comes from the second component drive, and so on, in round-robin fashion.
Mirror– This is also known as RAID-1. With this scheme, each of the drives is supposed to contain the exact same copy of data. This means that if you have an undamaged component drive, you should be able to just scan that to find your files (you will not need to create a RAID set).
Concatenated– This is not an official RAID level, but rather a way to make multiple hard drives appear as one big drive by concatenating them together. As data is read sequentially from the RAID set, it comes first from the first component drive, until the end of that drive is reached, then continues coming from the second component drive, and so on until the end of the last component drive.
The ordering of the component drives is mainly important for stripe and concatenated types. If this is wrong, the scan may find few or no good files. To alter the order, simply drag each drive in the list into its proper position.
For more information on RAID related recoveries, check out this blog.
Add Your RAID To Data Rescue
The Add RAID Set in Data Rescue allows you to simulate a RAID configuration based on the RAID functionality built into Mac OS X. This is helpful in case a RAID configuration fails to mount or be recognized as a single volume.
Please note that Add RAID Set does not attempt to fix or repair a RAID set. Instead, the RAID is configured through Data Rescue for the purpose of scanning for data.
In order to input your RAID configuration into Data Rescue, you will need to know how your RAID was originally setup; whether it was a striped or mirrored raid and how large the stripe size would be.
Once the RAID array has been added, it can be selected to scan for data. In some cases, data may not open properly when recovered because the hard drives were not arranged in the correct order. It is imperative that you select the RAID members in the correct order for the best results.
To simulate RAID configurations in Data Rescue, please follow these steps:
- Go to the “Data Rescue ” menu at the top of the screen and select “Preferences”.
- Click on the checkbox for “Enable Expert Features”, then close the Preferences window.
- Ensure you are within the “Detail View” for Step 1 to see the list of devices. If you are in Arena View (with the animated interface) click on the “Detail View” on the bottom left corner to change views.
- Hold the “Command” key and click on the Devices that belong to the RAID set. This should highlight multiple selections.
- Click on the “Expert” menu at the top of the screen and select “Add RAID Set”.
- In the RAID panel, rearrange the order of the drives accordingly from first device to last.
- Select the type of RAID the set was (Striped, Mirrored, Concatenated). Select the RAID Stripe Size if you know this information. If you are not using a Striped RAID, leave the Stripe Size as 32K. Click on “Continue” when done.
- You will notice a new drive to scan in your list as “RAID SET 1”. You may select this as your drive to scan. Proceed with selecting your scan method to search for your files.
Troubleshooting Your RAID Recovery
If data is not being recovered properly from the RAID, we suggest the following steps to troubleshoot the issue:
- If you are running on a Mac, you will want to adjust the Allocation Block layout and re-attempt the recovery until all options are exhausted or the files are recovered. When you open the Allocation Block layout tab you may see multiple options to select from. What this is doing is telling the software to start reading the data from a specific location of the drive. Depending on your setup, you may see only a single option or multiple options to select from the allocation tab.
Note: While in the Mac version, you can simply alter the starting point from within the scan results screen. In the Windows version, you will need to setup the offset and size information manually through the driver editor. This process is only recommended for advanced users who know their exact RAID configuration.
- Redefine the RAID set by using Add RAID Set, and drag to rearrange the order of the hard drives/volumes. Data Rescue does not currently support editing an existing RAID set. To change the configuration, you must define a new RAID set using the different parameters.
No Matter The Failure, Prosoft Has You Covered!
Data Rescue, quite simply, is the best performing Mac recovery software; especially when it comes to recovering files from a RAID. In the times of a simple failure, Data Rescue can recover your data from a RAID Array with no additional setup, yet still provides the in-depth tools needed to perform recoveries on Arrays that are more significantly damaged.
While the best practice to keep yourself safe from a data loss is having valid, active backups, Data Rescue (as well as The Data Rescue Center) have your back in times when you need to be rescued.