Update from Buffalo-Tech:
I had also created a ticked to Buffalo-Tech and yesturday (4-Sep) got a response which does not make me happy but which most propably closes the case. Direct quote below:
The behaiviour of your LinkStation Mini considered to be normal. It is a unit with passive cooling and laptop HDDs, so slump in speed after it's processor heats up is normal.
And a follow-up for my additional inquiry last night from Buffalo-Tech:
LinkStation Mini isn't high specification device. If you are intended to operate with large amount of data on daily basis, then you might need to consider more powerfull unit. If you move such amounts of data on ocasional basis, this unit will suffice your needs: in domestic environment over 80% of NAS bandwidth is bellow 1 GB.
When copying large files (5-30 GB) from Windows 8 laptop to Buffalo LinkStation Mini NAS drive, the copy transfer speed drops significantly after ~1 GB. The first GB is transferred 50.0000-65.000 KB/second, but after that ~1 GB transfer speed drops to 5000-6000 KB/second (<- almost 10 times less).
- Lenovo ThinkPad 431s Windows 8 64-bit Pro
- WLAN connection (with Intel Cerino Advanced 6235)
- ADSL/WLAN (ZyXel P-661HNU-F1) connected to Linksys Gigabit router (CAT6) ->
- LinkStation Mini 1T NAS connected to router (CAT6)
- Buffalo NAS mounted in Windows 8 laptop as network drive and working OK
Scenarios used for copying:
- Total Commander
- TeraCopy or
- Windows Explorer
-->> Always the same result => Copy speed drops significantly after ~1 GB transfer.
What's done / ensured:
- Cerino drivers updated to the latest
- WiFi powermgmt not "On"
- NAS has latest firmware
- ADSL has latest firmware
- No Antivirus slowing things down
When attached CAT6 cable -> router -> NAS box the end-result is again the same...