Nginx record length during disk IO

[Maxim Dounin]

Hello!

On Thu, Jan 12, 2017 at 12:18:28PM +0000, Nikolaos Tsipas wrote:

> Hello,
> 
> We're load testing nginx focusing on disk IO performance and we're trying
> to understand what's the record length used during caching operations. The
> reason why we'd like to know the utilised record length is that we could
> then use similar settings during our SSDs load tests.
> 
> We had a look at the code, specifically at the ngx_write_file method but we
> think that the record size used (i.e. sizeof(ngx_http_file_cache_header_t)
> is too small (~40 bytes) to be the one we are looking for.
> 
> Any useful information around that area would be appreciated as well as
> suggestions on where that information might be in the nginx codebase.

In most cases buffer size is probably what you are looking for.  
Depending on the particular operation it may be either 
proxy_buffer_size, or proxy_buffers, or output_buffers.

-- 
Maxim Dounin
http://nginx.org/