On 25.10.2008 8:48 Uhr, Hedley Roos wrote:
The usual Plone catalogs (portal_catalog, uid_catalog, reference_catalog and membrane_tool) all run above 90% hit rate if the server is up to it. portal_catalog is invalidated the most so it fluctuates the most.
If the server is severely underpowered then catalogcache is much less effective. portal_catalog hit rates will degrade over time. This is the situation I'm currently facing with on one site, but more servers will fix that.
It's quite easy to benchmark / load test with funkload. What I've found is that memcached is very light on CPU, but if the Zope processes are constantly using all CPU it is starved and runs into trouble. As long as you avoid that case (which would be fatal without catalogcache in any case) then everything works perfectly.
Have you measures the time needs for some "standard" ZCatalog queries used with a Plone site with the communication overhead with memcached? Generally spoken: I think the ZCatalog is in general fast. Queries using a fulltext index are known to be more expensive or if you have to deal with large resultsets or complex queries. Andreas