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Re: Moving MySQL to its own host

Hi there,

I think you should first look at adding memcached to the application
to accelerate it. But definitely, Apache+PHP and MySQL both require a
lot of CPU, so if memcached doesn't help or if you can't justify
rewriting the application you're using (assuming it doesn't already
provide memcached support), then that might be a next step worth
looking into.

If you decide to go the memcached route, first try putting all of the
applications on the same server. If there are still performance
issues, move MySQL to a different server--you can (and should) keep
Apache and memcached on the same server, since Apache is memory-light
and CPU-intensive whereas memcached is memory-intensive but CPU-light.

There is a lot of overhead for databases because they need to maintain
ACID compliance; thus they tend to be really disk-intensive. Apache
and MySQL will both compete for the disk as well as the CPU, which is
why there are scalability issues for large web sites.

To my knowledge, big web sites (such as Wikipedia) usually have a farm
of database servers running MySQL with replication enabled. Then they
have front-end web servers (possibly load balanced using the
appropriate mod_proxy modules for Apache) which also run memcached.
Memcached is a distributed caching system, so you can take advantage
of the memory of all servers to cache database data.

It all depends on your application and how many hits you are
receiving/predicting that you will receive. Not all applications
support memcached. Depending on the size of the application, I would
be willing to help you rewrite the application to include memcached
support, but it's been a long time since I've used PHP + MySQL, so you
may be better off asking somebody else.

Hope this helps.


Jonathan Yu

On 6/25/07, Simon <greminn@gmail.com> wrote:
Hi There,

We have a XenEnterprise Server running all debian sarge guests. One of
the guests is our client web server (Apache/MySQL/PHP). I have read
that there can be a performance boost in moving the mysql onto its own
host. Would this be worth looking at?



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