if you need access now you can install open media vault to a empty disk, boot it an access the dsm drives, omv should be able to use the raid/lvm
if you don't care about settings and plugins you can do a migration to different model like 3615 -> 3617, that way the system partition has to be completely rewritten, after that you can leave it or migrate back to 3615, your data should not be affected by this as its still just a migration
also you should use loader 1.02b not the older 1.02a