[TYPO3-english] How many sites can you run from one CMS?

[Philipp Gampe]

Hi Muriel,

Muriel le Pair wrote:

> But I'm still wandering about performance. What happens for instance if
> you clear all cache and 20 sites need to recache all there pages at the
> same time..

Short answer, avoid clearing all caches.
For bigger sites, you need to have a cache strategie that allows you to 
clear only individual caches. You might as well let changes apply only when 
the cache timeout is hit and the page is rebuild anyway. That is what 
Facebook does for example.

On top of that, even if you clear the page cache of all sites (only 
available to admin users), then you still only need to rebuild the pages 
that are requested. On other words, the load depends on your website and how 
frequent different pages are requested.

> I am wandering about the performance of 1 huge database versus 20
> smaller databases. If the table indexes are all setup right, and if the
> queries are optimized it would not make very much difference.
> But "TYPO3" tends to get all records and them do something with it
> ("select * from table" instead of pulling the correct data in the first
> place).

TYPO3 doesn't normally get all record where they are not needed. If you find 
a place where TYPO3 clearly gets more records than necessary, please create 
a new forge ticket about it or even provide a patch.
I would not say that all queries are optimal — we are far from that, but we 
should do quite well for things like pages and content elements.

You should watch the slow query log for big sites anyway and tune the 
indexes for frequent used queries.

As long as you do not do crazy joins without indexes, your queries should 
scale almost linear. That means it does not matter much if you use 20 or one 
database. Also you will eat up more network latency with more DB and you 
cannot use the caches as efficient (or maybe even more efficient). This 
really depends on your site and your usage patterns.

> And also I am wandering. Is it possible to separate them again?
> So for instance can you quickly export all data from 1 domain in a
> multiple website installation to another database? Never really looked
> in to that.

Separating them might be quite some work for huge sites as you need to 
resolve the recursive tree structure.
You will face the same problem if you want to combine two big sites.


You questions mostly boils down to how much synergies you want to use from 
maintaining several websites from the same system.

A single TYPO3 allows you to share assets (users, templates, etc.; could 
also be done via a file system level share for files) and to have stable 
cross-linking across domains.
On the other hand you create a single point of failure: administrative, 
security and performance wise.

Best regards
-- 
Philipp Gampe – PGP-Key 0AD96065 – TYPO3 UG Bonn/Köln
Documentation – Active contributor TYPO3 CMS
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