If it's unsupported hardware, as long as it speaks SNMP, you can most likely get at the data you need, though it may take a little research. Once you have the right MIBs to query, you can then use that information to write or adapt plug-ins to collect that data. In many cases, you can even integrate your cloud services into this monitoring by using standard SNMP on those instances, or by using an API provided by your cloud vendor. Just because you have cloud services doesn't mean you should trust all your monitoring to your cloud provider. The provider doesn't know your application and service stack as well as you do.
Getting most of these tools running usually isn't much of a challenge. They typically have packages available to download for most popular Linux distributions, if they aren't already in the package list. In some cases, they may come preconfigured as a virtual server. Configuring and tweaking the tools can take quite a while depending on the size of the infrastructure, but getting them going initially is usually a cinch. At the very least, they're worth a test-drive.
No matter which of these tools you use to keep tabs on your infrastructure, it will essentially provide the equivalent of at least one more IT admin -- one that can't necessarily fix anything, but one that watches everything, 24/7/365. The up-front time investment is well worth the effort, no matter which way you cut it. Be sure to run a small set of autonomous monitoring tools on another server, watching the main monitoring server. This is a case where it's always best to ensure the watcher is being watched.
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