This may be a slightly naive question, but why list both "500 web servers" and "...

simonw · on Feb 13, 2012

$ curl -i 'http://www.tumblr.com/ HTTP/1.1 302 Found Date: Mon, 13 Feb 2012 19:31:35 GMT Server: Apache P3P: CP="ALL ADM DEV PSAi COM OUR OTRo STP IND ONL" Location: https://www.tumblr.com/ Vary: Accept-Encoding X-Tumblr-Usec: D=15547 Content-Length: 0 Connection: close Content-Type: text/html; charset=UTF-8

$ curl -i 'http://assets.tumblr.com/images/favicon.gif?2 HTTP/1.1 200 OK Server: nginx/0.8.53 Content-Type: image/gif Last-Modified: Fri, 15 Apr 2011 22:13:30 GMT Accept-Ranges: bytes Content-Length: 635 X-Varnish: 1795992965 Cache-Control: max-age=2196224 Expires: Sat, 10 Mar 2012 05:35:30 GMT Date: Mon, 13 Feb 2012 19:31:46 GMT Connection: keep-alive

So it looks like their application is being served by Apache (and PHP), while their static assets are served by nginx behind Varnish.

silverlight · on Feb 13, 2012

Well, their assets are begin served from a CDN. Are they counting that in their server count?

  $ host assets.tumblr.com
  assets.tumblr.com is an alias for
  assets.tumblr.com.edgesuite.net.
  assets.tumblr.com.edgesuite.net is an alias for
  a1092.g.akamai.net.
  a1092.g.akamai.net has address 69.31.106.32
  a1092.g.akamai.net has address 69.31.106.50

retroafroman · on Feb 13, 2012

Good catch, that's along the lines I was thinking

riledhel · on Feb 13, 2012

Maybe the nginx servers are configured to serve static content, as reverse proxies or load balancers.

huxley · on Feb 13, 2012

Nginx can also act a proxy for mail protocols: http://wiki.nginx.org/MailCoreModule