Hi Francis,

> Can you tell from nginx logs whether the slowness is due to
> slow-read-from-disk, or slow-write-to-client, or something else?

Could you please tell me how to check this out?
My nginx logs do not contain this sort of information.

> Can you find any pattern in the requests which respond more slowly than
> you want? Certain browsers, certain times of day, anything like that?

Unfortunately, I didn't find any pattern. It's just sometimes loads in 2 seconds and in another time -- in 10-15 seconds. I mean same 300KB image within a couple of refreshes in a browser. I've tested the problem on different browsers and different times of day -- no luck.

> If you make the request from the machine itself, so network issues should
> be minor, does it still show sometimes being slow?

When I make request from machine itself, the image loads pretty fast.