System requirements

can anyone please suggest me what would be minimum server requirement for installing two IS instances and one UM instance on the same VM

Disk size:?

That depends a lot on what you want to do with it (Memory Demand from Concurrent Sessions, Service calls and related Data transformations, events to be cached and queued). Also depends if you install all in the same home or different, if you keep SPM running to maintain the instances and so on.
If you want to just run blank instances each 2 GB RAM is perfectly fine.
Disk Space is similar story. It depends on your traffic and space for data, code, logs.
Also would you install tools like TSA, Designer, UM EM etc. on the same box.
You also need some room during installation for TEMP data, product and fix images etc.
If you want it simple go for like 50 GB to be on the safe side. If you can mount maybe a drive that has all the install sources to your VMware then for sure the “minimum” disk that you keep with the image can be also much smaller.
How about an local database? :smile: