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Recover IBM RAID 5EE

Hardware and RAID Configuration

There were 3x1-TB drives in a RAID 5 setup. The drives were taken out of a 4-drive NAS whose brand the customer did not specify. (We usually do not ask for this information.) The fourth drive was damaged beyond repair.

Problem:

The customer did not provide any detail other than that “the shared data was inaccessible.”

Diagnosis:

  • RAID rotation analysis indicated the parity rotation is unlike a standard RAID 5 (i.e., backward or forward, symmetric or asymmetric). Each row contains two data blocks much like a RAID 6.
  • Metadata found on the drives suggested this was an XFS-formatted volume.
  • Further rotation analysis identified this as an IBM RAID 5EE. Under this scheme a 4-drive RAID 5 is equivalent to a standard 3-drive RAID 5 with a hot spare drive. However, in a RAID 5EE the spare drive also participates in the rotation.

Solution:

  • Although File Scavenger® no longer provides native support for RAID 5EE (due to lack of demand), it provides a much more powerful tool: custom raid rotation schema. This function gives the user virtually unlimited ways to define a RAID with any possible rotation scheme.
  • With a custom RAID schema created for this particular RAID, File Scavenger® quickly found the XFS volume and restored its contents. `

Result:

All files were completely restored with the correct name and folder structure.


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