Hardware:

• 1 Windows 2008R2 server containing 2 HBAs
• 2 SAN switches
• EMC VNX-5100
• 1 LUN presented over 4 paths (2 per HBA)
• no PowerPath or MPIO, so Windows host sees 4 vdisks and uses only 1 (with the risk of corruption)

Scenario:

After an unexpected reboot the host lost access to the data on the LUN and it seemed as if the vdisk was unformatted or at least corrupted.

• I checked the VNX, but all 4 paths were available
• “diskpart” showed the disk, but no volumes, so Windows people thought it was a “SAN issue” (which it wasn’t, of course)
• I tried enabling MPIO, but by default this host made the LUN (now visible as 1 vdisk instead of 4) read only
• After disabling MPIO I installed PowerPath (unlicensed) to be sure Windows only sees 1 vdisk instead of 4
• After the reboot I once again saw 1 vdisk and PowerPath showed 4 paths (of which 2 unlicensed)
• Still no luck accessing the data

the Community starts here

And here is where it gets interesting. The strength of the community is where you help each other and in this case the customer called me to inform me that since he had nothing to loose anyway he used “TestDisk by CGSecurity” and this tool actually discovers data patterns on disks and in the blink of an eye NTFS was found and the partition could be restored.

No format and restore of an earlier backup was necessary!