Re: [Xen-users] crazy SWAP and RAM idea

[Tom Brown <tbrown@xxxxxxxxxxxxx>]

On Fri, 8 Sep 2006, Luke Crawford wrote:

> 
> First off, let me say that I think virtuoso-style RAM oversubscription is a
> bad idea.

<snip> I'm not going to argue, I build all my xen boxes with lots of 
ram... but I made a similar proposal in response to a similar thread a 
while back about using tmpfs and sparse swap files in dom0:

   http://lists.xensource.com/archives/html/xen-users/2006-05/msg00961.html

> the problems with this setup are unavoidable in a shared-ram setup. The thing
> is, UNIX is designed to eat all available ram. 

yes, but UNIX knows the difference between ram and swap, it will _not_ eat 
all available swap unless it has to, it _will_ make use of
whatever "real" memory it has available.

> The other problem is one of business model;  if you give heavy users better
> service than light users, and you charge the same for both, in a rational
> market, all the light users would switch to a provider where they didn't have
> to subsidize the heavy users.  you would be stuck with only the heavy users,
> with nobody left to subsidize the system.

yeah, but if there was a real business model behind this, there would be 
enough RAM. The challenge is interesting and worth thinking
about, but should not exist in a real business world... But that isn't to 
say people won't do it. There are idiots and a*holes all over the planet 
that will take your money and give you trash or trash-service for it.

-Tom


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