[KLUG Members] Clustering

[Adam Williams]

>A friend of mine is looking into some powerful servers($50K-250K) 
>and asked for some recommendations. 

It is spelled I - B - M

>I suggested clustering since they'll 
>be using linux, but I've got some questions about it.
>Is clustering transparent to the apps?

It depends upon the app.

Things like LDAP, SMTP, or DNS cluster naturally,  they are built to 
cluster.

Web servers for statics pages obviously can cluster.  For "dynamic" 
applications you need a common session store provided by either LDAP, an 
RDBMS, or some other mechanism.

CORBA and other RPC based applications can cluster with a little thought,  
especially if you use a message and subscription oriented system like 
xmlBlaster.

File systems and RDBM(SQL) systems don't natuarlly lend themselves to 
clustering and usually need expensive prorietary hacks.  Microsoft DFS 
is only sort-of-distributed,  things like CODA and GFS are more 
distributed but not neccesarily clustered.

>Do applications have to be programmed to support it?

Yes, typically.  Although the if the layers underlying the application are 
"clusterable" this can be trivial.

>Has anyone here used clustering? If yes any info on setup/distributions?

I've clustered web apps and LDAP servers.

Clustering is a very vague term.  Do you mean High-Availability, load 
balanceing, etc..?

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