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I'm experimenting with memcache and installed it via these instructions on a dev box. I think I have it working.

The config file is mostly left at default:

# cat /etc/sysconfig/memcached
PORT="11211"
USER="memcached"
MAXCONN="1024"
CACHESIZE="64"
OPTIONS=""

My Question: What am I looking at here? How do I know how "effective" this set up might be? For example, when the sets row says "0.14/s; 773 sets (29.97%) of 2,579 commands", does that mean 29.97% of insert/updates where cached?

I'm having difficulty reading this report.

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Those are operations on your memcached server.

  • Sets: Data placed into cache by sets/second; by absolute number (by % of total commands); and a display of total number of commands. Sets are expensive (it represents needing to retrieve from your DB or other slower data sources) so you want this to be as low as possible, relative to gets.
  • Gets: Data requested from cache by gets/second; by absolute number (by % of total commands); by absolute number of cache retrievals (by % of total gets); by absolute number of cache misses (by % of total gets). Gets are the entire reason you employ memcache (to retrieve from fast memory rather than a slower disk/network) so you want this to be high as possible, relative to sets.
  • Counters: The number of increment/decrement operations performed on memcached counters.
  • Transferred: The ratio of read to written data. Since it's in absolute data amount, it gives you an idea of how much you're saving in reading from slow disk/network storage.
  • Per-connection average: The average amount of data and memcache operations made in a Drupal connection by gets/sets. The should give you an idea of how much memcache is employed on a Drupal request.
  • Available memory: The amount of memory used / available on the server. This is another metric showing how much you're utilizing memcache.
  • Evictions: The number of evictions or cached data removals from your memcached server.
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  • Thank you. Thank you. Upvote. Other things that I've heard while trying to gather data is that, if Evictions start increasing, I may need to increase RAM allocation for MC. Can you confirm this?
    – Rick
    May 22, 2015 at 13:55
  • I can't say I've experienced problem, but it makes sense; ideally, your cache should be covering the most requested data (e.g. cached front page, user sessions for large authenticate traffic, etc) and should stabilize around that; constantly increasing evictions could mean you don't have a large enough cache to cover the most frequently requested data. The memcache module lets you segment your servers by different tables so that might be another tact that helps stabilize your cache.
    – Shawn Conn
    May 22, 2015 at 15:35

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