[Zope] Re: Zope vs Plone: performance issues!

[Paul Winkler]

On Wed, Jan 25, 2006 at 11:47:21AM +0000, Jens Vagelpohl wrote:
> You should also look at increasing the ZEO cache size if you use ZEO.  
> This can be done in zope.conf as well. The ZEO cache is a disk cache.

+9 on that.  This is the cache-size setting *within* the <zeoclient>
section.  Fetching an object from ZEO over the network can
be MUCH slower than fetching the object from a local FileStorage,
depending on the network of course, but even on localhost ZEO has
some overhead that can be significant -- especially for loading
Images and Files.  If instead the object is in the ZEO cache, no network
request is made and the speed is basically equivalent to FileStorage.  

So, if you have a lot of objects that are read more often than
they are written, a big ZEO client cache can be very helpful.
It's still 20 MB by default IIRC, which is probably too small
for most "real" storage sizes.

The clue that you need to bump it up is in your event.log.
See how often there are lines like:

2006-01-25T10:30:59 INFO(0) ZEC:1-None-0 flipping cache files.  new current = 0

AFAIK, that means you've used up half of the specified cache size
since the previous time such a message appeared.  
There's no hard fast rule about how often you should want to see
a cache flip. If you see this once a week, you're fine but you could
get away with a smaller cache if you care about the wasted
disk space. If you see it every five minutes, you have a too small
disk cache.  Somewhere in between is good ;-)  I prefer to err on the side
of making it huge, and stop worrying about it.

-- 

Paul Winkler
http://www.slinkp.com