On 12/19/08 09:52, Tim Soderstrom wrote:
On Dec 19, 2008, at 11:49 AM, Roy Lyseng wrote:
For even better control, fire up a Solaris zone and a database
instance inside it. Then you can control IP, disk quota, memory
usage, CPU, etc, and probably simpler than partitioning the database
server...
Yeah, but that's basically virtualizing or user-mode segmentation type
stuff it sounds like. We can do that today but there's overhead in
managing all that. And MySQL starts competing with itself for
resources. What if you have, say, 200 customers on one box, for
instance. That's a ton of VMs or slices to mess around with. Granted,
the solution works today and it's less complicated than inventing a
new way of doing something like this, but you take a pretty big
penalty for doing that I'd say.
Since zones are really a userspace abstraction (think of it as an
additional column in the process table, though it's a lot more complex
than that), there really isn't much overhead. It's been a while since
I've measured it, but in the past if you were using native branded zones
(so lots of things are shared), and ran a minimal set of services it was
something like 14MByte of memory.
If you use other OS level resource controls which don't use something
like zones (like the project/task abstraction in OpenSolaris), there is
no significant memory penalty (other than that incurred for running
multiple drizzled's) and the CPU penalty is pretty small. In any event,
it'd be equivalent CPU overhead if resource controls were implemented at
the application layer. There's no free lunch here. :)
As I said earlier, it's pretty easy to think of use cases where it would
be better to do that at the application level (for instance, there are
plenty of buffers that could be shared more efficiently, if only you
didn't have that query-from-hell problem), so your point still stands.
The penalty just may not be as much as you thought it could be.
However, using VMWare or Xen or VirtualBox, you certainly have a lot of
things to manage and a lot of overhead. Heck, you're running a
scheduler and memory manager on top of a scheduler and memory manager!
Do you have a need for 200 drizzled processes on one box for multiple
customers? It'd be good to understand what you'd like to be able to do.
- Matt
--
Matt Ingenthron
http://blogs.sun.com/mingenthron/
email: [email protected]
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