I have used this same unit and have had drive crashes before. Did you have the unit configured as RAID 0 or RAID 1?
If RAID 0, then the data would be distributed between the two disks in such a way that both are required to retrieve the data.
If RAID 1, then each disk would store a copy of the data.
If you had two disks installed, and only one failed, and you were using RAID 1, you can simply install a second disk and the unit will rebuild the array automatically. I’ve done this before and it works fine without losing data.
You may want to discuss the issue with a professional data recovery company before going further, as you could damage the data beyond repair by attempting to fix it.
However, if you were on RAID 0 and one disk died, your data is probably lost, unless you want to try to dump an image of the drive to another working drive and re-add it back to the system to see if it can reconstruct part of the data.
If the unit only contained one disk installed, I have had excellent results using R-Studio to recover from various types of drives. It supports several Linux and Windows filesystems.
Good luck! I sincerely hope you kept good backups
NOTE: before doing this, exhaust your other recovery options, as this may completely corrupt the array!