Practical limit to number of jails on a given host?

[Doug Barton]

Howdy,

Thinking about implementing a poor-man's virtualization solution with
lots'o'jails, and wondering what people think about the practical limits
of such a system. I realize that part of the answer is going to depend
on CPU and RAM, so let's assume for the sake of argument that the answer
to that bit is, "Lots of both."

So first question is, is there some sort of hard-coded limit somewhere?
If not, what is the largest number of jails that you've created
successfully/reliably on a system, and what are the specs for that system?

On a related note, what are the limits in terms of mount points on the
system and/or jails? I'm thinking of a fairly typical "nullfs mount the
system, devfs, and 2 or 3 NFS mount points" per jail type of situation.

And finally, has anyone run into trouble with a large number of IP
addresses for the jails? ISTR that way back when, the IP addresses
associated with a particular interface were stored in a linked list, so
as you added more you would start seeing O(N) slowdown on a lot of
network stuff in the kernel.

Any thoughts or advice along these lines will be greatly appreciated. :)


Doug

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