Image Hosting

[Indo Php]

Hi Maxim,

With this config, my iowait in increasing.  38.4%wa

before that, maximum is about 15%wa




________________________________
From: Indo Php <iptablez at yahoo.com>
To: nginx at nginx.org
Sent: Thu, October 14, 2010 9:39:29 PM
Subject: Re: Image Hosting


Hi Maxim,

I'm trying your suggestions

Here's the config that I used right now
worker_processes  10;
worker_rlimit_nofile 50000;
error_log   /dev/null;

pid     /etc/nginx/logs/nginx.pid;

events {
        worker_connections  50000;
        use epoll;
}

http {
        include       mime.types;
        default_type  application/octet-stream;

        client_header_timeout           1m;
         client_body_timeout             1m;
        client_header_buffer_size       24k;
        large_client_header_buffers     32 256k;
        send_timeout                    1m;
        ignore_invalid_headers          on;
        keepalive_timeout               5;
        output_buffers   1  128k;
        directio   1m;
        server_tokens   off;
        location ~* 
^.+\.(jpg|jpeg|png|gif|ico|css|zip|tgz|gz|rar|bz2|doc|xls|exe|pdf|ppt|txt|tar|mid|midi|wav|bmp|rtf|js|swf)$
 {
                aio on;
                directio 1;
                access_log      off;
                expires         max;
        }

        location / {
                aio  on;
                directio 1;
                try_files $uri $uri/ /index.php?$uri;
        }


        location ~ \.php$ {
                fastcgi_pass   127.0.0.1:9000;
                fastcgi_index  index.php;
                fastcgi_param  SCRIPT_FILENAME $document_root/index.php;
                 include        /etc/nginx/conf/fastcgi_params;
        }



________________________________
From: Maxim Dounin <mdounin at mdounin.ru>
To: nginx at nginx.org
Sent: Thu, October 14, 2010 8:46:57 PM
Subject: Re: Image Hosting

Hello!

On Thu, Oct 14, 2010 at 12:26:59PM +0000, iptablez at yahoo.com wrote:

> Actually the image size is arround 100KB each. The server is running in 250Mbps 
>traffic. 
>
> I already described the disk I'm using is scsi 15K RPM in raid 0

Basic tunings you have to apply when serving static which doesn't 
fit into memory are:

If you use sendfile:

- Make sure your OS uses appropriate read-ahead for sendfile to 
avoid trashing disks with small requests (and seeks).  For FreeBSD 
8.1+ it should be enough to set read_ahead directive in nginx 
config (0.8.18+).

http://sysoev.ru/nginx/docs/http/ngx_http_core_module.html#read_ahead
(in Russian)

Using bigger socket buffers (listen ... sndbuf=... in nginx 
config) may help too.

- If serving large files - make sure you use appropriate 
sendfile_max_chunk to avoid blocking nginx worker on disk for too 
long.

- Consider switching sendfile off if you can't persuade it to read 
large blocks from disk.

If not using sendfile:

- Tune output_buffers (again, to avoid trashing disks with small 
requests and seeks).  Default is 2x32k, which will result in 4 
disk requests for 100k file.  Changing it to 1x128k would result 
in 2x memory usage but 4x less disk requests, this is probably 
good thing to do if you are disk-bound.

In both cases:

- Using aio may help a lot ("aio sendfile" is only available under 
FreeBSD) by adding more concurency to disk load and generally 
improving nginx interactivity.  Though right now it requires 
patches to avoid socket leaks, see here:

http://nginx.org/pipermail/nginx-devel/2010-October/000498.html

- Using directio may help to improve disk cache effictiveness by 
excluding large files (if you have some) from cache.   Though keep 
in mind that it disables sendfile so if you generally tune for 
sendfile - you may have to apply output_buffers tunings as well.

It's hard to say anything more than this without knowing lots of 
details.

Maxim Dounin

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