It was hinted out that the SSD while does cannot perform at 2.1 GBS you see.  Linux by default is using ram and sending a single to DD that it completed, although it is still in ram not on the disk.  It take a few more ms to complete the write. 
The proper way to test a disk with dd is to add "conv=fdatasync"That will informs the system to return the actual write speed after the memory is synced to disk.  Try this on the host and you should see 300-400MBs.
So why can't you get the same performance in a VPS, there is an issue with double caching, i.e. cache in the VPS then cache on the host.  The VPS tries to take care of this but not very good.  As always recommended cache=none is actually the best for the virto driver. This ensures that the VPS gets direct access to the array and always ensures when the system thinks something is written it actually is.