Asus RT-AC68U poor performance of samba/smb only in 5GHz

[Unforgiven11]

Hi,

i'm using Asus RT-AC68U and USB-AC56 on a pc with Ubuntu 14.04 an the asus driver installed. On both bands 2.4 and 5GHz i get normal throughtput measured with iperf and normal pings.
In 5GHz mode I get very poor performance when trying to access the shares of a samba/smb server connected via gigabit lan to the Asus RT-AC68U. It takes much time to see the contens of folders and streaming of movies is also impossible. But in 2.4GHz it is working fine.

Does someone have an idea how to deal with it?

Regards

 

[Unforgiven11]

I also tested the Netgear R7000 and same thing here: poor performance when accessing samba share. I solved the problem by switching to NFS, I get a much better performance here.