Storage LRU Expiration Age -- what does it mean and is it accurate?

What does the value "Storage LRU Expiration Age" represent (from
cachemgr ?

In my mind, it represents the age of the oldest object in the cache
based upon current cache utilization. One thing that confuses me is
that this value bounces a lot for me. I usually see it at .9 days, but
I just checked it and with a five minute average of 11 http
requests/second it just showed me a Storage LRU Expiration Age of 40
days! It's not unusual to see it at .9 days and check it again 10
minutes later and see it at 5 days.

In my mind that means that this counter is either totally inaccurate or
is based on such a short snapshot of cache activity that it might as
well be totally inaccurate. Am I off base here?

My cache size is pretty small -- 750MB -- due to lack of RAM. I'm
planning on upgrading the hardware to much more ram and a seperate,
softupdate-mounted disk for the cache. Would a small disk cache size
have anything to do with this value? If the figure was at all accurate,
I would expect that the LRU time would stay permanently at a low figure
during the day.

(FWIW, I just checked and in the time it took to write this message my
LRU time is down to 1.25 days.)
Received on Wed Aug 09 2000 - 12:41:17 MDT