Hello,
For my garden irrigation, I have an openHAB2 system running on a Pi 3B+ (Linux installation). For other, newer applications, I have an openHAB5 system on a different Pi 3B+ (Linux Trixie installation). Is it possible to integrate the openHAB2 system into the openHAB5 instance e.g. via remote access?
Regards Ulli
Why not run irrigation off your OH5 Pi?
well … there is no real reason to change the openHAB2 irrigation system. It’s running without problems for years.
“never touch a running system” 
/Ulli
looks good, I’ll try it.
Hopefully it will support all the stuff that is used on the openHAB2 system like DBaccess, PI GPIOs etc.
/Ulli
Well, obviously there is: you asked for it. You would be touching it, one way or another.
So why not do it right in the first place?
Co-location with the garden may make sense for the remote Rpi3 based on the technology used. I use the remote binding for coverage of certain z-wave devices off a remote Rpi3b. All that might be required on the remote is getting a token for API access.
The real reason for my post is a caution about the OH5 Rpi3. IMO that could be pretty limited for OH5 (64-bit O/S) and the more you grow that system, hardware limits could appear. I think the remote OH binding is pretty “light”, assuming you just pick up item states via the API, but if you start to migrate rules, etc. it could get dicey. My main OH instance is now on a Rpi5 4GB. You could be fine, but just something to keep an eye on.
It is strictly Item based. With the add-on installed on your OH 5 instance, you’ll have a Thing with one Channel that represents each Item on the OH 2 system. You can link those Channels to Items on your OH 5 instance and those Items will be commanded and updated when the corresponding Items are commanded or updated on the OH 2 instance. If you command or update the Item on the OH 5 instance, they will be forwarded to the OH 2 instance.
Not really as the Remote openHAB add-on is only installed on the OH 5 instance. But it is touched in that commands and updates to Items that reside on the OH 2 instance could now come from somewhere else (i.e. the OH 5 instance).
But the Remote openHAB add-on does not required modifying the configuration on the OH 2 instance nor does it require and changes to installed software nor add-ons.
But one reason I could see to not want to just move everything to the RPi 5 is the GPIO. The RPi 2 likely needs to be relatively close to the wires that control the irrigation valves which may not be a great location to host the rest of the home automation.
I’ll second this caution. An RPi 3 is generally not enough to run OH 5. The limitation is RAM. You will get a much better experience over all with a RPi 4/5 with at least 2 GB RAM or a used/refurb thin client or mini-pc (these days the prices are roughly the same).
Exactly! The installation is in the garden shed.
The other actual IT equipment is located in the utility room in the basement.
Well, as I said: I’ll try it.
Thanks for the hints to OH5. Actual it runs. But the installation is quite new and not every planned function is programmed yet. I will keep an eye on the resources.
Pay attention to the load (note load is not how much the CPU is being used, it’s how many processes are stuck waiting for a resource) and swap. If OH seems to have delays between when an event happens and OH reacts, or it starts beign killed due to out of memory exceptions you need more RAM.