You are correct in how elements are calculated. Each node, volume, and interface counts as an element and each of those together is your total number of elements. So if you're maxed out you must be at or above 12k elements, is that right? One of the biggest things you can do in terms of elements is cut back on the amount of interfaces you're monitoring (if you haven't already). By default, when you run a discovery or add a node, SolarWinds will automatically monitor every active interface but in most environments this isn't necessary. I'm an Engineer with Loop1 and we provide professional/consultative services for SolarWinds. When I look to clean up an environment I always start with looking at what interfaces are being monitored. Things like Null0's should be removed and in some cases loopbacks can also be removed can be removed right away. Generally speaking you want your uplinks and other critical interfaces, other than that you typically don't need to monitor every active interface. I have a bit of free time this morning if you have any questions or I could send a bridge over to show you what that process looks like. Hope this helps!
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