The system they were stored on is a 12x 3TB disk HP DL360 server running Server 2016. The disks are/were in RAID 50 array, giving a total of ~28TB total storage.
We also use MS Data Deduplication (NTFS) on the server.
About a month ago one of the disks failed and took down the entire array (nobody knows why, but it happened)
Put in a replacement disk, array rebuilt itself - BUT essentially it looks like the NTFS fat table got corrupted, so the Virtual disk won't be recognised
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Steps I have done so far to try to recover.
Installed R-Tools
Scanned drive
Found the Drive letter and the missing folder structure, together with the file names of 17k files that I want to (initially) recover
Did a test recovery of about 500 Photos (JPGs), but each of the JPGs appears to be corrupted in some way (i've tested about 100 so far

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Any ideas what I can check next?