[geeks] Solaris 10 zones - interesting blog

[Scott Howard]

On Wed, Sep 22, 2004 at 04:01:25PM +0000, Lionel Peterson wrote:
> > He is testing how many zones he can run at once on it.  So far he is
> > up to 54 zones, and is adding more (he started IPs at .200 and just
> > got to .254, so he needs to mess with his scripts).
> 
> That's neat - I wonder if there is a hard limit, becuase I suspect it
> should be able to handle any number of zones, provided he can rig up

I've seen the number 4000 thrown around, although I don't think this is
an actual physical maximum.  Looking through the code the only limit I
can see is that the zone ID can't be greater than 9999, which would mean
no more than 9999 zones running at once (zoneid's can be re-used so it's
a concurrent limit, not an overall limit).

About 6 months ago I setup a few hundred zones on the one machine - from
memory someone pushed it to well over 1000 around the same time.

> sufficient virtual interfaces for them - he'll probably run out of IP

>From memory Solaris supports something like 8192 virtual IPs per interface,
so this isn't a limitation.

> address space first... I would think that respinse time would suck, as
> everything would swap in and out of local memory, but if all the zones
> are inactive (as it seem they are), the delays caused by the swapping
> may be unconnected to the number of zones running (they are only swapped
> in/active when an "echo" request is received over the interface).

This is of course relative to the amount of memory, but...
>From a performance point of view zones make no difference to the system
(unless you're using the fair share scheduler on top of them). There's
still only one scheduler, and it still schedules processes the same,
regardless of which zone they are in. The only difference is that instead
of having 1 copy of (for example) inetd running you have 2, 30, or 9999
copies of it running. Depending on your config that may still only mean
one copy of the inetd binary in memory, but each will have it's own local
memory (heap/stack/etc) so memory usage will obviously be up somewhat.

But let me say, if you think zones is cool, wait until you see zones+smf...

  Scott.