[OT] Virtualization (WAS: UNIX V7)

Liam Proven wrote: There is VMWare ESXi which is also freely available for download, that runs on the raw hardware. So while there'll still be some overhead, you remove most of the overhead of the host OS - but of course you're replacing the host OS with a lighter weight one that's designed just for running guest OSs. Either way, using VMWare tools on the guest is an important part of running VMWare - if you want performance. Otherwise, VMWare has to emulate actual hardware devices, which is much more work than simply transferring the I/O requests to the hypervisor. There was some controversy over the Intel VT stuff - it turns out it does run slower than doing it in just software. Most of what VMWare does is trap & emulate supervisor level instructions, but there are a few opcodes that it can't do this with - don't remember the exact ones, so what it does there is to scan the binary for those opcodes and replaces them. The biggest limitation I find to VMWare and stuff like it is memory. You really do need a lot of RAM to get usability. Not surprising. If you want to run 2 or more Operating Systems at the same time, you need enough memory to make each OS and whatever Apps you plan to run under them not page. If you can't do that, don't run things virtually. Typically there's enough CPU cycles, but not enough memory. For most situations, but not all. As with everything, there's always a price to pay, but there are benefits too.