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My datadisk with important data crashed for unknown reason. I didnt do any dangerous actions. It is internal disk WD Red 40EFRX (4TB). When I run testdisk, it shows size of device only 1,8 TB, so any attempt for recovery cannot be done. I have searched answers, but otherwise disk shows as simple raw. My Win7-64 disk manager see disk in proper size, so at least firmware looks to be undamaged. Formatting would resolve usability, but not recovering data. I acquired R-Studio and just now I am in process of creating disk image before taking any other actions. Estimated time to finish is still 2d22h, In testdisk, with incorrect disk size I cannot search for partitions (there was only one), because it don't see damn whole thing. Any thoughts, how to proceed? Updating firmware seems useless to me, because Win shows it as proper 4TB. Error is somewhere else.
Attaching screenshot of testdisk and disk manager.
ufikus

Can you check the disk jumpers ? LBA48 may be disabled.
You should also use the manufacturer tools to check the disk capacity (HPA and DCO size)
You can also boot from a Linux LiveCD/USB and use the Linux version of testdisk to check if the problem is Windows specific or not.