VM with disk on SMB3 share has good read but bad write speed

Hi All,

I've got a Hyper-V Node connected to a Windows FileServer (all Server 2016) via 2x10Gb on the node and 4x10Gb on the FileServer. 

During testing I've removed all NIC teaming with no effect but bot machines are doing multichannel as expected.

But when I now run CrystalDiskMark on the VM it shows up to 1800MB/S _read_ but only 150MB/R _write_.

This can be also watched on the network side as the FileServer NICs are not show much traffic during write.

Any Idea how I can track that down? Measured already Read/Write on the fileserver but this is good (RAID100 SSD with 6K MB read and 1k MB write).

If I just manually copy some files to the fileshare the transfer runs around 600MB/S.

BG

Daniel