Unsure about proxy_temp_file_write_size to prevent upstream response buffering

[Dave Cheney]

For large dynamic responses generated by our application occasionally  
they are being buffered to disk

2008/01/29 14:21:13 [warn] 19297#0: *12289266 an upstream response is  
buffered to a temporary file /opt/local/var/run/nginx/proxy_temp/ 
3/50/0000123503 while reading upstream, client: 4.224.132.81, server: www.redbubble.com 
, request: "GET /people/redbubble/journal/206322-redbubble-post-card- 
everyones-an-artist HTTP/1.1", upstream: "http://172.16.0.72:8005/people/redbubble/journal/206322-redbubble-post-card-everyones-an-artist 
", host: "www.redbubble.com"

In this case the resource is

[dave at crimson ~]$ curl -I http://www.redbubble.com/people/redbubble/journal/206322-redbubble-post-card-everyones-an-artist
HTTP/1.1 200 OK
Server: nginx
Date: Tue, 29 Jan 2008 03:22:08 GMT
Content-Type: text/html; charset=utf-8
Connection: keep-alive
Set-Cookie: _session_id=223812df7b7e519d8ca3b2a6540b7016; path=/
Cache-Control: private, max-age=0, must-revalidate
Content-Length: 73827

73827 bytes long (before compression)

I have

proxy_temp_file_write_size 128k

set to 128k, which I thought would buffer up to 128k of data in memory  
before writing it to disk.

Cheers

Dave