Hi there,
we are currently doing consultancy work for a bigger Zope-based CMS
project (lotes of users, lots of concurrent editors/write). Plone and
CMF are basically what we are looking into right now. It is well-known
that Plone is poor on concurrent write. It is basically impossible
creating more than 3-4 objects per second on decent hardware. On
observation we made was that Plone causes transaction size of 30k-100k
per each new object (this is also true trivial changes on existing
content objects). So I thought this might be a limiting factor and
looked at CMF. The transaction sizes under CMF are much smaller -
typically between 2k and 4k for new objects or object changes which is
looking good at the first glance. However the transaction size does not
seem to have any impact on the number of simulataneous writes.
I wrote script simple script like this:
results_folder[randint(1,500)].invokeFactory(Document, some_id)
where result_folder is a btree based folder containing 500 other empty
btree folders.
Running 'ab2 -n 100' against the site would create 100 new documents
distributed over the subfolder (avoid conflicts errors here).
The performance was nearly as bad as with Plone. It was hard getting
more 4-6 new objects per second out of a standard CMF site (2.1,
zope.schema-based types). Even variations of the zserver-threads and the
ab2 concurrency level did not help much.
hmm....so why is CMF here nearly as bad a Plone. In Plone we know that
everything is indexed various times (also in CMF I think) but Plone has
much more indexes and metadata compared to CMF. A request in Plone goes
through much more layers than in CMF....I am currently clueless
interpreting the results. My current interpretation is: a custom
CMF-based implementation of a CMS will be comparable slow/fast as an
out-of-the-box solution?!
Thoughts?
Andreas
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E-Publishing, Python, Zope & Plone development, Consulting
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