Peter Daum wrote:
I can confirm, that the problem must be on the client side: Meanwhile, I installed a 64bit-system on the machine with the big disks (unfortunately also my only machine where I have this option): Now, I can access large nbd devices exported by this machine from the same machine via loopback, while other machines (with 32-bit-systems) still show the same problem.
Yes, greater than 2TB works on 64-bit but not 32-bit. It's due to a limitation in the NBD kernel ioctls (which nbd-client uses to set up the nbd device). You might be able to increase the NBD block size (using NBD_SET_BLKSIZE ioctl) and get > 2TB working on 32-bit -- I've not tried.
-- Paul