What NAS-performance is needed for openHAB with KNX?

Hallo everone,

For some time I have tried to use openHAB. On my desktop the program runs good. But I don’t want to leave my desktop on forever. So I have tried to run openHAB on my NAS; I have a Synology DS213, 512 MB. And I have tried to run openHAB on a Raspberry Pi 2. On both the NAS and the Raspberry, after some time, a few hours until two days, openHAB stops. I got messages: “skipped tunneling request with rvc-seq ##”.
In this discussion group I have seen others with the same problem. One of the others is using a ABB Ips/S2.1 gateway. I am using a the KNX-router Hager TH 210. So I don’t think it is a router problem. A suggestion is made that it is a matter of performance. So I am thinking of buying a more powerfull NAS. But before spending money I like to know what performance I need.
Therefore I want to ask: who of you uses openHAB for a KNX installation smoothly on a NAS and what is the type of that NAS. (And perhaps the same question for a singleboardcomputer like a Raspberry).


Meanwhile I can give a partly answer myself.

There is not a performance problem with my NAS or Raspberry.

I found out that my KNX/IP-router sometimes “forgets” a sequence number. A KNX router gives every message a sequence number. Every new messages must have a sequence number one higher than the one before. OpenHAB uses Calimero for the basic knx functions. Calimero checks the sequence number of the messages. If the sequence number has a unexpected value,the message is ignored and Calimero waits for a message with the right sequence number. If the KNX router skips a value, Calimero will wait for a long time for the correct number. In the meantime all the incoming messages are ignored. The knx binding effectively stops working.

Other programs does not seam to have a problem. But, for example OpenRemote throw an exception when it recieves a wrong sequence numbers. The exception closes the connection and a new connection is opened. KNX keeps working.

I know now what the problem is, but not the solution. For now I have changed the Calimero software a little bit. When the sequence number is one higher than the expected value I add one to the expected number before comparing it. This “solution” seems to work for me. So at last I can go forward with OpenHAB.