I have an older model Hubitat (got it right before they released a hardware update, oops!) and I’m thinking about taking advantage of the Presidents Day sale.
Do any of you use two Hubitats in tandem, or would this be an upgrade-then-migrate sort of situation?
I have a C-3, a C- 5 and a C-7 all connected with HubMesh. Works amazing!
I have a C-5 with zigbee devices and a C-7 with z-wave devices. They are connected by HubMesh. No complaints!
Me too!
I ran C5s and C7s together for a month or so (Hub Mesh) with no problems.
c5 and c7 here
I had a C4 meshed with 2 C7's for a while. Never had any issues. Eventually retired the C4 because it was running hot frequently and now just have 2 C7's.
When running two hubs do you keep the zwave radio on in both hubs?
You can, but you end up with two separate networks. One hub Zwave can't repeat for another hub, for example.
It depends how you are using them. In my instance I have one hub dedicated to apps, rules, etc. with no actual devices (That was my C4) on the other I have my Zwave and Zigbee devices. Since I had no devices , I pulled the Zwave stick . The C4 was replaced by a C7 a few months ago. I have both the Zwave and Zigbee radios shut down on that hub. I don't know that it is absolutely NECESSARY, but I figure if it isn't necessary, there really is no reason to have them on and adding to the noise in the various meshes.
One question, why would you need 2 hubs? You can use zigbee & z wave on one hub together, and the hub can handle a lot of automations & devices. So what benefit would 2 hubs bring?
Couple of reasons people do it. Off load processing. (devices on one, rules on another). Cloud on one, local devices on another. Large home where you can have one at strategic areas of the house (so one mesh is handled on one side, and another mesh is handled on the other and they talk to eachother through hub mesh) and a myriad of other reasons. Hell people have 3 or 4 and even one just for testing something before it's brought into the working system.
For me it was because my old C4 at times would become non resoinsive, even with my tiny meshes. When I moved into a new home and had to start over anyway I left rules, apps and basically the processing on the C4 and shut down the radios, and the devices on a C7 linked by hub connect. I bought two C7's intending to further seperate the zwave and zigbee, but got lazy and put them on one hub. I eventually replaced my ISP's router with my own which messed up my hub connect and I couldn't get it working again so I replaced it with hub mesh which has worked great! Actually, it is quite a bit easier to implement than hub connect, and is more flexible. Eventually I began to notice the C4 was running on average around 200 to 220 degrees (my C7's are in the high 90's to between 100 and 114) so I decided to retire it and replace it with the extra C7 as the processing hub. Do I think one C7 could handle it? Sure. But I have gotten used to this split set up. I'm actually contemplating adding a 3rd hub for cloud integration so I could seperate those from the local network if necessary, or to use as a test bed.
Is there advantages separating and putting Zigbee on C5 and Zwave on C7?
The Zigbee radios are the same, but the C-7 has the Z-wave 700 chip which is supposed to do cool things like support S2, have longer range, and create ghost nodes 
. My guess is @aaiyar didn’t want to migrate his Zigbee mesh over for zero benefit.
Myself, I have 2 HE hubs with separate Zigbee networks; one for well behaving repeaters, locks, and sensors, and the other for lights.
I have a similar setup as @aaiyar - An advantage is issues with one will not directly effect the other - load is somewhat distributed depending on how many apps/devices you have. For C3 / C4 I would probably just use it for cloud / network apps and devices and maybe Zigbee. That way you are an easy restore away from migration. With the C3/C4 there are known memory issues - slow degradation over time - the JVC is 64 bit which for a low end device like HE can be problematic.
"By location" hubs is another great way to do this as well - balancing the load and resistant to complete system failure but I would prefer to have 2 of the same type of hub for this.
I have several S0 devices (the older Zooz 4-in-1 sensors) that don't play well with the C-7 and several Ring gen2 contact sensors that don't work on the C-5. That said, my Z-wave networks are not super-reliable, so I'm trying to figure out which way I should go.
You can pair the zooz stuff without security if you use a z-wave stick. That said, leaving them on the c5 works just as well. You can have multiple z-wave networks.
Is there any guidance on the maximum supported devices per hub? Let’s say on a C7.
I guess as many have indicated the number of rules and cloud integrations will also crest load. How does one know when it’s time to add a second hub?
This can depend on so many factors it's hard to say with any certainty. There have been members that have over 200+ devices on one hub and are still running happily with rules and everything.
A second or third hub could be employed if the area of the devices is large - say for a detached shed or garage or just a large property.
Otherwise maybe adding a second hub by device "type" - Like my setup - I have a C7 for Z-wave devices, a C5 for Zigbee devices, and another C5 for cloud/network apps and devices (Alexa, Flume, Lutron, etc).
Chances are you'll be fine with what you have and thanks to HubMesh add something later on if necessary. Using the "lite" versions of RM whenever possible and limiting 3rd party apps also helps with resource utilization. I prefer to keep my rules off hub by incorporating a companion server running Node-Red..
You can also monitor your hubs free memory and other attributes using @thebearmay's excellent HubInfo driver.
Download the Hubitat app
