how nginx cache manager delete file cached on disk

[Maxim Dounin]

Hello!

On Thu, Aug 09, 2012 at 07:02:13PM -0700, Don Zhou wrote:

> We used nginx proxy to cache lots of static files. Our monitoring tool
> showed that the write I/O on the server spike once a day on 4am GMT time
> and server will slow down significantly because of the high IO. I couldn't
> find any cron that can cause this. I am guessing it might be the nginx
> cache manager was clearing the disk cache once a day.

No, it's not nginx cache manager.  It removes files as soon as 
they become inactive and/or max_size reached.

> We have cache setting like: proxy_cache_path  /cache levels=2:2:2
> keys_zone=cache:2000m inactive=1d max_size=400000m;
> 
> Any idea? Thanks!

Something like "top -mio" / iotop might be helpfull.  Time 
suggests most likely it's some daily periodic task.

Maxim Dounin