Web service throughput slow and clipping

Question

We've been seeing the slow web throughput performance that clips between 4 and 5 KB/s. We've tried upping the simultaneous connections from 500 to 1024. I've also read through the post at http://discussions.apple.com/thread.jspa?messageID=4468345&#4468345 and I wasn't able to gain anything useful from the suggestions there to track it down.
The system is a Mac Mini w/ a 1.66 MHz core duo and 2 GB Ram. It's connected to the net through a 3 MB/s line. It is a relatively low use server but it does host several virtual domains (about 8), with the busiest getting a few hundred visits a day.
The graphs look like this:
1 hour - http://www.ncimedia.com/graphs/Throughput_2.jpg
24 hour - http://www.ncimedia.com/graphs/Throughput.jpg
Any help you can provide in tracking down the problem would be greatly appreciated.
Thanks,
Tom

Answer 1

I don't see a problem here.
It is a relatively low use server but it does host several virtual domains (about 8), with the busiest getting a few hundred visits a day.
Let's say, all 8 sites get 200 visits per day, that's 1600 hits per day, or about 66 hits per hour, or roughly one hit per minute. If most of the sites don't get that many hits, it's even lower.
1 hour - http://www.ncimedia.com/graphs/Throughput_2.jpg
The graph isn't showing actual throughput. It's showing average throughput. Assuming that the 1 hour graph is made up of 60 one minute buckets, what you're seeing is the average throughput in each one minute window. Some of the windows have no traffic at all (remember, there's only one hit per minute, on average). Even the windows that have traffic won't show much because the average transfer is less than 1 minute in duration.
Taken another way, assume that in a 1 minute period, you serve 1 page at 500kbps and it takes 2 seconds to transfer. No other hits come in during that time window, so on average you're serving 1000 kilobits per minute, or 16 kilobits per second. 16 kilobits per second translates into 2KB/s (the graph is measured in KB/s, or kilobytes per second, not kilobits). Now you're in the range of your graph.
What I'm getting at is that the scale is low, because the traffic to your sites is low and the server is idle most of the time.
We've tried upping the simultaneous connections from 500 to 1024
That won't help. Most of the time you have less than 1 active connection. Telling Apache it can sustain 1024 connections doesn't matter since it doesn't need anywhere close to that many.
All that limit does is tell Apache how many active connections to handle. Above this it rejects new connections until an existing connection slot opens up.
So it appears that I'm limited to 5 simultaneous connections
That's not what the Server Status page is telling you at all.
Even though Apache is told it can have a maximum of 1024 (or 500, whatever) connections, it doesn't actually run that many all the time. That would be a waste of resources. What it does is open a limited number of processes that run all the time (known as MinSpareServers). These processes will handle the first n active requests. Once that limit is reached Apache will spawn additional processes (up to the maximum defined) to handle additional traffic.
So what you're seeing is the 5 active processes waiting for a connection. The remaining 1021 connections haven't even been fired up because they're not needed. Given the traffic level on the sites it's unlikely that you're using more than one or two connections simultaneously.
If you want to use more of those apache processes, drive more traffic to your sites