[redhat-ccm-list] multiple instances on one set of infrastcructure

[Daniel P. Berrange]

On Thu, Feb 19, 2004 at 05:54:47PM -0500, Richard Li wrote:
> The main limiting factors here would be RAM and CPU speed. I would check 
> to make sure your database and application server are not running into 
> resource limits first. If not, then adding additional application 
> instances and/or schemas to the existing machines should not present any 
> problem (depending on your projected server usage).

Yes, as a rule of thumb you should allow 1 GB of RAM per CCM instance
minimum. A second rule of thumb is that (once the basic DB is tuned
correctly & any dodgy SQL optimized) most CCM sites are bottlenecked
at the app server level, so you can easily expand capacitiy by adding
further app servers. 
 
> This is definitely a good way to go if you have a large number of 
> relatively low-traffic sites, since maintenance costs can be reduced. 
> The tradeoff is scalability and reliability (one site can bog down 
> another one).

Actually, if its for several low traffic site, your likely better off 
implementing a 'virtual hosting' type solution, whereby one CCM instance
servers many sites. Some of the benefits of this:

  * Only a single server intsance to maintaine
  * Authors can publish to many sites without having to continually
    login / out of each CMS
  * Share same piece of content across many sites
  * Search engine can pull results from many / single site.

Of course there is the counterpoint, basically all eggs in one basket,
but this can be addressed at a number of levels, with multiple app
servers load balanced, database replication, nightly DB snapshot to
standalone backup system, etc.

> Internally, we do not use multiple database schemas for different 
> production instances. Instead, we run multiple database instances on the 
> same machine. This gives more isolation between applications.
> 
> Rick Cecil wrote:
> 
> > The current infrastructure on which our production environment is 
> > maintained (ccm 6.0) consists of a solaris app server running resin 
> > and a solaris database server running oracle.  In the interest of 
> > quickly creating some customized and discrete section presentations, 
> > we are considering running multiple application instances and multiple 
> > database schemas on the same hardware.  Does anyone have any 
> > experience with a similar concept to offer me some of their feelings 
> > or experiences pro or con?

There is not so much in it for the database server, but for app servers,
solaris/sparc hardware gives a really terrible price/performance ratio in 
comparison to intel/linux. In my experiance a entry level Dual P111 Xeon 
2.4 GHz can comfortably deal with mulitple CCM instances on a single box, 
but the equivalent priced sparc netra would struggle to provide acceptable
performance even for a single instance.

Dan.
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|=-             Daniel P. Berrange  -  berrange at redhat.com              -=|
|=-   Red Hat, 338 Euston Road, London, NW1 3BT.  +44 (0)7977 267 243   -=|
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