Re-create Deleted or Damaged Disk Array (RAID) Virtually
There are many reasons for a Redundant Array of Independent Disks (RAID) system to fail (RAID controller failures, software RAID emulator errors, etc.). Active@ UNERASER provides an easy way to assemble array disks together and make damaged or deleted data accessible.
You can combine together a disk that was previously used as a part of a RAID system in a temporal (virtual) disk array. With this virtual configuration, you are able to perform all drive file recovery manipulations as though it is regular drive. You can even to create a Disk Image for the whole RAID and store it to the safe location.
It is important that you specify the parameters of the RAID system that you know existed before the fault so that you can virtually reassemble the same system.
It is also important to list the disks in the correct order when making a virtual disk array. In most cases, the correct order is unknown. The only way to discover the correct order is to try all available combinations until you reach the one that works. If you are dealing with only two disks, it is simple. You have only two ways to arrange the order. If there are three disks, you must try a maximum of six combinations. If there are four disks, 24 combinations, and so on...
Each time you try a combination, write down the order you are trying, click OK and check the results by trying to access and scan the newly-created virtual RAID that is added to the list of Local System Devices. If you don't see your data or if there was an error during virtual array creation, mark this one as a failure and try another order of disks in array.
To create a Virtual Disk Array (RAID):
To open Recreate Disk Array (RAID) dialog, in the Action menu, choose Recreate RAID (Virtually)...
To choose a supported RAID type, in the Virtual Volume Type area, choose one of the following:
Stripe Array (RAID-0) — Data located in stripes (blocks of size 32KB, 64KB, 128KB, etc.) distributed between two or more drives
Mirror Array (RAID-1) — Data on two disks is identical - provides complete data duplication (or mirroring)
RAID-5 Array — Data located in stripes distributed between two or more drives with parity control
Span Array — Data located contiguously on one disk then on another disk, and so on...
To select disks from a list to create a virtual disk array:
In the Available Disks list, select a device (or disk image)
To add it to the Selected Disks list, click Add
Repeat steps a. and b. for every disk in the original array. If one of the disks is physically damaged and not accessible, and if you have selected RAID-0 or RAID-5 in step 2, from the Available Disks list add Damaged Device instead of the named damaged disk
To change the order of disks in the Selected Disks list, select a disk name and click Up or Down to change its position in the list
To indicate the size of the stripe block, in the Options area, type the size of the block in kilobytes in the Stripe Block (RAID0 and RAID5) field. This is applicable only to RAID-0 and RAID-5 arrays. Standard values are 32Kb, 64Kb, 128Kb, 256Kb. If you are not sure, try each size until you get the correct one
To indicate the offset and the size of the device, measured in sectors (each sector is 512 bytes), in the Disk Area to Use in RAID (Sectors) area, type the values in the Device offset and Size fields. In most cases, the default values are acceptable. Some RAID controllers use only part of the disk surface. For example HighPoint 370 uses the first 100 sectors on the first drive for its own system information. In this case you would specify the offset as 100 sectors
Click OK to start Virtual Disk Array reassembly process
In the Local System Devices list, a new Virtual Disk Array device node appears. You may treat this new node and its contents the same way that you treat other device nodes in the list.
You may follow the standard steps to scan the Virtual Disk Array node, then search for files and folders to be recovered. You may also create a Disk Image of the whole Virtual Disk Array to work with it later on.
When dealing with Span Arrays, you may get the size of a Damaged Disk a couple of ways:
Go to the hard drive manufacturer's web site and look for the model.
Look for the device geometry label on the top of the physical drive. If you find it (it is not always there) you can multiply the parameters C*H*S (Cylinders * Heads *Sectors per Track) to get the number of sectors. For example, Samsung SW0212A has the following: CYL 4092, HD 16, SEC 63, 2.1GB. Multiply 4,092*16*63 to get 4,124,736 sectors. To calculate the disk size, multiply 4,124,736*512 = 2,111,864,832bytes = 2.1GB. We just confirmed the size 2.1GB. The size is marked on drive label and that proves that our calculations are correct.
When dealing with RAID5 Arrays, if the most frequently used Left Async type does not work for you, you may try some several different types of building array:
Left Asynchronous (the most frequently used in hardware RAIDs)
Left Synchronous (used in the most software RAIDs, based on LDM)
You may consult your RAID controller manufacturer to determine the proper RAID5 type being used in hardware.
This document is available in PDF format, which requires Adobe® Acrobat® Reader (Free download):