There is a similar discussion (Network/Raid performance on ESXi5) here but as it is marked 'answered' I cannot add any more stuff
Anyway, the answer (set useDNS to no) does not change the problem.
As mentioned in the other discussion, for some reason the speed of a file copy via ssh (e.g between two esxi hosts) does not exceed 11MB/s
Copy speed via virtual machines (also via SSH) on these hosts result in much higher speed
So, whats holding the host access ssh connection back?
I use a shared Dell iDrac connection (server is Dell R610). I wonder if this has impact
regards
Daniel