# Slow streaming due to high %utilization!

**URL:** <https://www.ruby-forum.com/t/slow-streaming-due-to-high-utilization/245505>\
**Category:** NGINX\
**Created:** [June 5, 2013, 7:57am UTC](https://www.ruby-forum.com/t/slow-streaming-due-to-high-utilization/245505 "2013-06-05T07:57:46Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![Rafa\_F](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/r/958977/32.png) [@Rafa\_F](https://www.ruby-forum.com/u/Rafa_F)\
**Post date:** [June 5, 2013, 7:57am UTC](https://www.ruby-forum.com/t/slow-streaming-due-to-high-utilization/245505/1 "2013-06-05T07:57:46Z")

</div>

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…

---

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**Author:** ![shahzaib12](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/s/90db22/32.png) [@shahzaib12](https://www.ruby-forum.com/u/shahzaib12)\
**Post date:** [June 5, 2013, 8:48am UTC](https://www.ruby-forum.com/t/slow-streaming-due-to-high-utilization/245505/2 "2013-06-05T08:48:02Z")

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Hello,

On Wed, Jun 5, 2013 at 1:56 AM, shahzaib shahzaib  
[removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid)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  
> aio[http://nginx.org/en/docs/http/ngx\_http\_core\_module.html#aio](http://nginx.org/en/docs/http/ngx_http_core_module.html#aio)directive.  
> 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  
directio[http://nginx.org/en/docs/http/ngx\_http\_core\_module.html#directio](http://nginx.org/en/docs/http/ngx_http_core_module.html#directio)directive.  
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)

> [mailman.nginx.org archive](http://mailman.nginx.org/mailman/listinfo/nginx)

​No other idea.

## Hope I helped,​

_B. R._

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<div class="post-metadata">

**Author:** ![shahzaib12](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/s/90db22/32.png) [@shahzaib12](https://www.ruby-forum.com/u/shahzaib12)\
**Post date:** [June 5, 2013, 10:06am UTC](https://www.ruby-forum.com/t/slow-streaming-due-to-high-utilization/245505/3 "2013-06-05T10:06:20Z")

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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.