Serving big files at constant rates

[B.R.]

Hi,

A recent thread kept my attention recently:
http://forum.nginx.org/read.php?2,226327

I don't have such a big trouble, but I don't see how to solve it.

My server usually serves small files suchas classical web pages.
On a particular location, though, I serve big files (around 100MB+).

I noticed that when those files were served, there was 'bumps' in the
transfer rate, whether the trasnfer stalled for 1s or the transfer rate
downgraded to 500Kb/s during the same period.
Those bumps were monitored server-side, so it is not some trouble in any
network in the middle.
I ensured that the only service using significant bandwith would be Nginx.

I guess I am experiencing some disk I/O speed limitations.
Thus, I tried to use aio on that location:
aio on;
directio 4m;
output_buffers 1m; (I tried 512k first hand)

The bumps are still there, appearing randomly but quite often and regularly
on the long shot.

What kind of I/O trouble is that?

Thanks,
---
*B. R.*
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