Shell Programming and Scripting

I have 2000 odd servers (may of which are virtualisations) and if we want to run a script against all of them or distribute files/install software to all of them, we currently perform a simple for loop against a managed list of our servers called SLIST

Code:

for host in `cat SLIST` ; do
   ssh $host 'run command'
   scp some-files $host/opt/
done

obviously there are some additional checks in there as well, but this is basically what it does

The problem is, doing the simplist thing takes the best part of half a day.... (to run through the servers in SLIST)

Id love to hear the methods that you guys use to distribute stuff out to large environments or run scripts on multiple machines...

ive seen some utilities like shmux etc, are these any good in an enterprise environment? is there a better way I should be looking to perform this task

Any thoughts would be great

Assuming you have a passwd less ssh connection between all 2000 servers i can sugest one method to reduce time..
split your SLIST file into 10 or 20 small files and invoke your script parrellely providing it diff SLIST files... its like multistreaming your process..