Slow streaming due to high %utilization!

Server NGINX
1

Hello,

   We're using nginx-1.2.8 to stream large files size 1G but found

the
slow stream with high utilization of harddrive using command “iostat -x
-d
3”

  Device:         rrqm/s   wrqm/s     r/s     w/s   rsec/s   wsec/s

avgrq-sz avgqu-sz await svctm %util
sdc 0.00 444.00 78.67 7.00 18336.00 3608.00
256.16 3.28 39.17 11.02 94.40
sdb 0.00 0.00 0.00 0.00 0.00 0.00
0.00 0.00 0.00 0.00 0.00
sda 0.00 0.00 0.00 0.00 0.00 0.00
0.00 0.00 0.00 0.00 0.00

16G Ram
8X CPU E31240
HDD SATA

Following are the main nginx configuration :-

http {
include mime.types;
default_type application/octet-stream;
#tcp_nopush on;
client_body_buffer_size 128k;
client_header_buffer_size 128k;
client_max_body_size 1200M;
keepalive_timeout 10;
ignore_invalid_headers on;
client_header_timeout 3m;
client_body_timeout 3m;
send_timeout 3m;
reset_timedout_connection on;
#gzip on;
access_log off;
include /usr/local/nginx/conf/vhosts/*;

}

Would be very thankful If someone could help me with better
configuration
of nginx to reduce HDD-utilization.

Best Regards…

2

Hello,

On Wed, Jun 5, 2013 at 1:56 AM, shahzaib shahzaib
[email protected]wrote:

  sdb               0.00     0.00    0.00    0.00     0.00

0.00 0.00 0.00 0.00 0.00 0.00
sda 0.00 0.00 0.00 0.00 0.00
0.00 0.00 0.00 0.00 0.00 0.00

16G Ram
8X CPU E31240
HDD SATA

​The best way of serving large files is to use asynchronous transfer to
avoid blocking disk requests.
To do so, have a look at the
aiohttp://nginx.org/en/docs/http/ngx_http_core_module.html#aiodirective.
The default behavior uses sendfile, which sends file in a
synchronous fashion​.

Note 1: On Linux, aio will work for writing requests only if activated
alone. To activate asynchronous read requests (which seems coherent to
your
use case, since you stream files - I understand yo usend them, thus you
read them), you need to activate the
directiohttp://nginx.org/en/docs/http/ngx_http_core_module.html#directiodirective.
Refer to the aio documentaiton (link above) for details.

Note 2: Using directio will automatically disable sendfile. If you don’t
use it, you’ll need to deactivate sendfile manually.

You might also wanna have a look at your output_buffers (once again see
the
aio directive documentation) to improve large files buffering.
I read around that buffers large enough (>= 4MiB) are usually advised
for
big files (splitting them in less parts). Maybe you would like to make
some
tests for your specific use case to find the most appropriate values.
The number of those buffers also have an impact: too much buffers
consumes
RAM for nothing, whereas too little of them will slow down requests by
creating an artificial bottleneck.

Following are the main nginx configuration :-

client_header_timeout  3m;

​By default, Nginx sets gzip to off. Depending on the content you stream
and since you seem to have a nice CPU potential (you didn’t provide
information on CPU usage, you’ll need to see if you have room for gzip
compression there), you might wanna activate gzip to reduce the amount
of
data transferred, thus lowering the transmission time at the cost of a
more
sollicitated CPU… if your content provides room for a sensible
compression efficiency (once again, it depends on your specific use
case).​
​No need​ for it if the benefit is 1% ;o)

nginx Info Page

​No other idea.

Hope I helped,​

B. R.

3

Thanks for co-operation B.R but i’ve got to know that aio doesn’t work
well
with linux centos and i already used it once with one of our content
servers for serving large-files. I noted that after enabling aio, the
svctime reduced but %util increased upto 20% using command iostat -x -d
3

Regarding gzip compression, i am afraid that our content server is used
for
large videos serving as well as conversion which consumes 80% of cpu
resources and gzip compression would overwhelm the cpus.

Also trying to figure out that how nginx works with the terms
asynchronous
and synchronous ?

Best Regards.