Currently virt-v2v tries to reduce the amount of page cache used when writing out the disk image to the target storage. It does this by enabling the cache=none option in nbdkit-file-plugin.

Documentation of this option is here:
https://libguestfs.org/nbdkit-file-plugin.1.html#PARAMETERS

While we still believe this option works fine, we have found that when the backing storage is Dell PowerMax 8000 (only) this causes data corruption. The precise reason has not been root caused, but use of this option is known to trigger the corruption.

Therefore we think we should remove use of this option from virt-v2v for now, until the root cause is understood.