Odd cache behavior

Igor Sysoev is at rambler-co.ru
Sat Oct 3 13:22:59 MSD 2009

On Fri, Oct 02, 2009 at 01:07:24PM -0400, Jim Ohlstein wrote:

> Hello,
> I'm seeing odd disk usage statistics for my cache. The cache is 
> primarily of small files (images, javascript, and css) and sits on a 
> 128GB SSD using ext2 file system mounted with "noatime" option. The 
> cache is all that the the drive is being used for at this time.
> The attached graphs were generated by Munin using df. The data from du 
> correlates closely with df when run manually.
> As you can see, periodically, with no set interval, disk usage rises 
> gradually, and then drops precipitously. I don't see anything out of the 
> ordinary in the error log. The cache serves about 2.8-3 million requests 
> per day, up from ~2.2-2.4 million one month ago.
> The cache config is:
> fastcgi_cache_path /falcon/cache levels=1:2 keys_zone=one:1024m 
> inactive=1d max_size=80g;
> where the SSD is mounted as /falcon.

As I understand /falcon is used solely for nginx cache ?
Could you monitor inode usage also ?
Did you restart nginx in the times of the drops or not ?
Currently I have no idea why it may be.

Igor Sysoev

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