From: Joe C. <jo...@sw...> - 2002-01-01 21:22:38
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Just chiming in with my .02, as someone who has done a lot of research in this area. For what you are describing, you do not need or even want independent Linux kernels running. You want a solution like what FreeVSD or OpenVDS offers...these are chrooted administration and serving environments where each customer has an 'admin' account on their own IP. They can modify their own servers to their hearts' content, install their own software, etc. They don't 'see' the other users on the server, and their service configurations (httpd, MySQL, etc.) is separate from the other users--they can even run different versions and options of Apache in their chroot environment. UML is /also/ really cool for a similar task--but certainly not for individual administration tasks. UML would be cool as a step up from the VDS/VSD type of service, in that not /only/ could the user have their own Apache and MySQL and such things, they could have an entire computer to layout as they like. Installations from standard OS vendor packages (RPMs, debs, etc.) would work as though they have their own server. Users and groups and all the normal system stuff would act just like on a standard dedicated server. This sort of thing isn't /quite/ possible in a VDS environment, though you can get close. Performance of a VDS will be better than from a UML system as well--thus a much larger number of VDS clients can be installed on a single server than UML clients. There are folks running about 700 sites on FreeVSD machines (with much tweaking). FreeVSD seems to be evolving into a commercial product called ProVSD, but it is located at: http://www.freevsd.org OpenVDS is at Savannah here: https://savannah.gnu.org/projects/openvds/ OpenVDS is developed by a group of volunteers who got a bit angry over the apparent lack of interest in Open Source the FreeVSD parent company were showing. I don't know if volunteers will keep pace with FreeVSD, or not. But both are usable today as a solution to the problem you describe. But...By all means experiment with UML as a 'premium' virtual dedicated environment for your clients (billing appropriately to make up for only having 30-60 UMLs on a honking big 4GB box instead of the several hundreds or even thousands that a traditional virthost can provide or the several hundred that a VDS can offer). I plan to use it for that purpose, one of these days. Gil Vidals wrote: > Hi, > > I appreciate Jeff's quick responses. A responsive > forum sure makes things more enjoyable! > > My goal is to have 250 UMLs running and to provide ssh > connectivity to 250 customers. Each customer's UML > will have to have > > Based on Red Hat 7.2 Kernel > * ssh > * ftp > * http compiled using DSO w/ php and mod_bandwidth > * webmin (for administering their private uml space) > * postfix (or sendmail) > * bash (with basic functionality) > * vim > > If I upgrade the RAM to 1GB, then I can assign 1 MB of > RAM to each UML. Is that enough to keep the UML from > swapping out so that it is responsive when called > on??? On the other hand, I suppose it would be > reasonable for the UML to swap in the first time, but > remain in memory while the web site is being hit or > other processes are being run on the UML such as > Webmin. > > If it sounds doable in theory, I'm willing to give a > try. I want to be reasonably sure I have a chance of > getting this to work before going crazy on it. I'm not > a kernel hacker by any means, so I have to rely on > your help in working through this. > > Gil@Vidals.net > > --- Jeff Dike <jd...@ka...> wrote: > >>gil...@ya... said: >> >>>1) What is the minimum RAM that will be needed to >>> >>run each UML? >> >>It depends on what you want them to do, and what >>kind of performance >>and responsiveness you need. >> >>There are two ways of talking about how much memory >>a UML needs. One >>is how much "physical" memory you assign it on its >>command line. >> >>UMLs running a lot of stuff are obviously going more >>memory than ones >>that aren't. The memory requirements should be >>similar to a physical >>machine doing the same thing. >> >>The other is how much memory the host needs in order >>to run the UMLs at >>whatever level of performance you want. The two >>aren't necessarily closely >>related to each other. If you are happy with having >>lots of UMLs swapped >>out on the host at any given time, then you can >>assign much more total >>"physical" memory to the UMLs than you have memory >>on the host. >> >>The downside is that they will likely be swapped >>out, and the responsiveness >>of a swapped out UML isn't so good until it's back >>in memory again. >> >>On the other hand, if you want all your UMLs to be >>in memory all the time, >>then you need as much memory on the host as you've >>assigned to all of the >>UMLs. (Although a loophole here is that if a UML >>doesn't touch all its >>memory, it won't all be allocated on the host, but >>Linux tries to use all >>the memory at its disposal, for caching files if for >>nothing else). >> >> >>>2) Is it possible to have one instance of apache >>> >>running on the server >> >>>and then have a configuration file installed in >>> >>each UML? I prefer to >> >>>have one httpd parent daemon, if possible, >>> >>otherwise, each UML has to >> >>>have their own private httpd, which will take more >>> >>RAM. >> >>I think that's doable, although I don't fully >>understand what you want. You >>could have the config files live on the host and >>exported to the appropriate >>UML. hostfs sounds like a decent way of doing the >>export. >> >> >>>3) Has anyone successfully deployed up to 250 or >>> >>so virtual hosts each >> >>>in their own UML? >>> >>The most I've heard of doing real work is ~20 on a >>modest PC (that's one >>of the case studies on the UML site). >> >>250 sounds a bit far out unless you have a truly >>beefy server in mind as >>the host. >> >>It sounds like you want the UMLs to be used for site >>administration by your >>customers and not to do serving. That will cut down >>on the requirements >>on the host. Even so, I think you can do many tens >>of UMLs, but not >>hundreds. -- Joe Cooper <jo...@sw...> http://www.swelltech.com Web Caching Appliances and Support |