Khalid Baheyeldin wrote:
> There are many big sites running Drupal and they have low page
> generation times (I have seen page generation times as low as 16
> milliseconds, average is 100-300 ms, with spikes to 600 ms).
>
> I personally know sites that do 930,000 page views a day, 59,000
> per hour using the above averages.

Thanks for the figures. What kind of hosts is that? What kind of caching?

In this case, it is a dual Opteron, 2GB dedicated, with no caching (yes, none!)

> Even on a relatively inexpensive Xen VPS (forget Virtuozzo or OpenVZ,
> they are slow), performance is really snappy.
>
> Because Drupal uses a lot of queries, it will be slow on shared hosts
> that lump together lots of sites and their databases, or on sites that
> have no PHP accelerators.

Thanks, I see. Is there anyting one can do to improve the situation when
one has a Drupal site on a shared host (except turning on Drupal caching)?

Find a better host is the short answer, specially if they have absurd caps
on CPU seconds you can use, amount of memory per process or
number of database queres.

The long answer is to try to find what real bottlenecks your particular host
has. Are they CPU starved? Are they database bound?

Install the devel module to see how many queries you have per page. Try
to cut down the number of modules you use.

Read a bit on the tools and resources here
http://2bits.com/articles/drupal-performance-tuning-and-optimization-for-large-web-sites.html