Ready to take the plunge into VMware? Like the idea of server consolidation but don’t know where to start? Here’s a quick primer, that might save you some research time.
Hosts and Guests
A Host is the base operating system of the physical server. A Guest is an installed virtual machine server. Generally speaking, the Host operating system is independent of the Guest operating systems, and once you have a host system running, you can run just about any operating system inside of it as a Guest.
Choose Your Platform and Virtualization Software
I combined these two tasks because platform is often dependent on virtualization software. Xen uses Unix/Linux based Hosts, VMware uses Windows or Linux, Microsoft VM uses a Microsoft base. Parallels has products for Windows, Linux and even Mac, and seems to be growing, but it remains to be seen where their products will eventually converge focus. Parallels products include Parallels Desktop for Mac, Parallels Workstation, which seems to be comparable to VMware Workstation, and Parallels Virtuozzo, which was SWSoft’s virtualization product. SWSoft’s aggressive marketing led to fairly deep penetration in the large hosting provider markets, so Parallels may have a shot at serious competition in this arena.
I know that being RHCE-certified means I should be rocking Xen, but I haven’t gotten my feet wet in it yet. I have, however, heard good things about its virtualization methodology. Ask me again in a couple of weeks, or feel free to discuss your experiences in comments.
My primary focus has been VMware. There are things I really like about VMware. I’ve been happy with performance so far, even in just the Workstation version, but especially under ESX. There are plenty of comparisons out there between VMware, Microsoft Virtual Server and/or Xen, but they are largely unscientific and anecdotal, and some don’t even specify which version of VMware is being used. The consensus seems to be that Xen is faster than VMware (probably Workstation) which is faster than Microsoft Virtual Server.
For workstation-based Virtual Machine solutions, my preference is to house everything on a Unix or Linux base, with no graphical interface, reducing overhead. More specifically, my current preference is a CentOS base, and I’ll tell you why. Under Red Hat and Fedora-based systems, VMware generally needs to compile the VMMON for the working kernel. Because Fedora kernel updates are so frequent, this means that you will be running vmware-config.pl frequently to recompile vmmon, etc. CentOS is directly derivative of Red Hat Enterprise Linux (RHEL), and features far fewer kernel updates. There is a trade-off, of course, if you need to use things on the same PC which require newer kernel features. I have heard from a colleague that Debian’s approach may be a bit more sane in terms of its packaging these things (NVidia drivers have the same underlying problem of needing a recompile during kernel upgrades, and Debian may have conquered that as well) but again, I have not yet experienced it. I have a fundamental shortage of servers and time to do this type of research.
If you’ve read this far, you’ve read enough for today. I’ll continue this at a later date.
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