On Wed, Feb 07, 2007 at 03:30:07PM +0000, Steffan Davies wrote: > > At least two of the machines in question would be running fairly > heavily-used MySQL instances (currently a 5G or so database) with > replication and the others are Apache/Java app servers for the most > part, so likely to perform better if given copious RAM. > > None of it's completely monstrous, but possibly a bit much for a virtual > box, especially as if all goes to plan we'd like to be doing a lot more > traffic than we are now in the next few months. > > Thanks for the idea though. > If RAM is the biggest concern, then Xen might be the way to go. The reason is that while Xen doesn't guarantee CPU (unless you are on a multi-CPU machine and you associate the particular domU and no others to a particular CPU), and doesn't guarantee disk I/O, it *does* guarantee RAM. So, unlike vserver and some other virtualization solutions which allow the host domain to "oversell" or overcommit RAM, Xen uses only dedicated RAM. So, if a machine has 1 GB RAM and you reserve 256 MB for the dom0 host and 256 MB for each of three domU guests, the three guests will each get 256 MB all to themselves. I'm running some Xen servers for hosting my own services and some clients. Bascially, unless you see the need for monstrous disk I/O needs, a Xen domU will probably get you what you need/want for less than a dedicated machine. The other nice thing is that there is no specific hardware in the domU (it's all generic), you can find someone who has the latest/greatest hardware (though I am not sure you need it) and put a minimal dom0 with the rest of the machine allocated to a domU for just your machine. Then you can run Sarge on very new hardware, as long as the dom0 was Etch or another distro like RHEL5 or the newest SUSE, that supports the new hardware. Regards, -Roberto -- Roberto C. Sanchez http://people.connexer.com/~roberto http://www.connexer.com
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