On Wed, Sep 08, 2010 at 04:51:17PM -0500, Kevin Grittner wrote:
- David Kerr <dmk@mr-paradox.net> wrote:
-
- > Hmm, i'm not following you. I've got 48 cores. that means my
- > sweet-spot active connections would be 96.
-
- Plus your effective spindle count. That can be hard to calculate,
- but you could start by just counting spindles on your drive array.
We've got this weird LPAR thing at our hosting center. it's tough
for me to do.
- > Now if i were to connection pool that out to 15 people per
- > connection,
-
- Where did you get that number? We routinely route hundreds of
- requests per second (many of them with 10 or 20 joins) from five or
- ten thousand connected users through a pool of 30 connections. It
- started out bigger, we kept shrinking it until we hit our sweet
- spot. The reason we started bigger is we've got 40 spindles to go
- with the 16 cores, but the active portion of the database is cached,
- which reduces our effective spindle count to zero.
That's encouraging. I don't remember where I got the number from,
but my pooler will be Geronimo, so i think it came in that context.
- > that's 1440 users "total" able to use my app at one time. (with
- > only 96 actually doing anything). not really great for a web-based
- > app that will have millions of users accessing it when we're fully
- > ramped up.
-
- Once you have enough active connections to saturate the resources,
- adding more connections just adds contention for resources and
- context switching cost -- it does nothing to help you service more
- concurrent users. The key is, as I mentioned before, to have the
- pooler queue requests above the limit and promptly get them running
- as slots are freed.
Right, I understand that. My assertian/hope is that the saturation point
on this machine should be higher than most.
Dave
