First, see this page in the documentation:
It’ll help clear up a few common naming convention differences in Virtualmin from what you’re used to in cPanel.
1. I'm not a hosting company but I do have a dedicated server that houses a few dozen of my own domains. I only really use 6 of those domains. Will I have to buy the 10-50 domain license to to have a bunch of simple domain accounts for my parked pages? Do sub.domains.com count against the domain license too?
If by "parked" you mean "alias" (see above), then no. Virtualmin licenses pay no attention to alias domains. Only domains that provide different content consume licensed domains.
2. The virtualmin.com demo seems to be just like the virtual min I installed on my server. Is the virtualmin.com demo the Pro of Free version?
Professional. But, Virtualmin GPL and Professional share the same codebase–Professional just has a few extra features on top. The Install Scripts feature is probably the most popular reason people upgrade, but there’s also some nice features for Ruby on Rails and Django developers, and a few nice enhancements in the API. There is a comparison chart showing the differences between GPL and Professional (and cPanel and Plesk) here: http://www.virtualmin.com/compare.html
3. Being that vm virtual servers limit the memory and process limit of domains, is there any way to take the limits off for certain domains? Does anyone have any experience with high traffic sites on virtualmin?
Of course. Every virtual server (get used to calling “domains” virtual servers when talking about Virtualmin…domain is abused as a term in this field, and makes it hard to talk about the differences between mere names and the actual entity that includes web, mail, DNS, and other services) has it’s own resource limits. I believe resource limits are another area where Virtualmin Professional adds some bonus capabilities (and I’m pretty sure most of the related charting tools are Pro only, as well).
Spend some time with Server Templates, to get a feel for how Virtualmin "thinks" about stuff like this. A Server Template is a set of limits and features that can be applied easily to a new virtual server…once created, you then modify those limits on a per-virtual server basis.
I don’t know what qualifies as “high traffic”, but there are at least a few sites running Virtualmin that get more traffic than our Virtualmin.com server–a couple of reasonably well-known Web 2.0 websites are managed with Virtualmin behind the scenes. Twitter used Virtualmin for its first year or so of existence, Evan told me so himself…which was awesome to hear…I don’t think they use it anymore, however, as they’re on entirely custom infrastructure now, and aren’t hosted at Joyent–I don’t think Virtualmin had anything to do with Twitter’s scaling problems, as I think our stuff was already out of the picture by the time things started getting rough for them. As for hard numbers that I do have, Virtualmin.com hosts doxfer.com, and parts of Webmin.com, among other things…altogether it gets about 120,000 visitors per month and a few hundred thousand page views. I don’t consider this high traffic, of course, just another point of reference.
Generally Virtualmin is not going to be related to scaling. Your application(s) have to be built to scale, or you aren’t going to scale–there’s nothing an admin panel can do to make your application use a sharded database. But we have added some scaling related features over the years in response to users scaling problems. ndb_cluster memory tables in MySQL are supported by Virtualmin, and that makes it easy to drop your session storage and other small-but-has-to-be-wicked-fast tables into a fast memory store that’s spread across many machines.
4. Is Virtualmin load balance friendly? If one of my sites gets large traffic spikes, can I grow a solution with Virtualmin?
Yes, and no. Mostly no. Again, scaling is a problem that Virtualmin can’t really do a lot about–if it were just static data, we could obviously add some simple replication features and call it done. But, who needs to load balance for static data? Apache can serve tens of millions of pages a day from a single modest server, if it’s all static. It’s when the database and application get involved that scaling becomes challenging and requires multiple machines…and that’s where things also become impossible for a tool that isn’t built into the application to solve the problem. If you search the forums, you’ll find several threads about scaling…and we’ve all kind of hashed out various ideas on the subject. There’s not a great answer that we can really provide, unfortunately (because the only answer that works is, “build your apps to scale, and they will scale”).
We are thinking about it, however, and do plan to keep pushing forward with the stuff that we can do at the control panel level. Like better multi-db management, replication of static content and meta-data, and management of services running on different machines (already possible for DNS and databases).
5. Have any of you switched from cPanel? What do you think about virtualmin?
I’d say about 10-20% of our customers have come from cPanel. Possibly a lot more and we just don’t hear about it (the cPanel migration tools are pretty good now, so problems don’t come up as often as they used to–so maybe half of our new users are coming over from cPanel and we never hear about it because the migration went of without a hitch, I’m not sure!).
Anyway, I’ll leave it to others to talk about what they like and don’t like about the change. cPanel is a product with a lot of history and a lot of good development behind it…so I imagine there are probably still a few areas where people miss something good from cPanel. I’d kinda be curious to hear about those things, myself, so we can fix it.
BTW-The Tiger theme is not a Virtualmin theme, and will leave a large swath of functionality either hidden or completely inaccessible. I love the theme, as well, but so far I’ve been unable to convince David to work with us on making it into a fully Virtualmin capable theme. At this time the only full featured Virtualmin theme is Virtualmin Framed Theme. I recommend you use it for your Virtualmin systems. (It’s getting prettier with every release, don’t worry…it’ll be awesome soon.)