[CentOS] rpmsave files and pagasus

Hello

I just upgraded Centos, and now doing some post upgarde task to make 
sure every thing is fine.

First of all, it seems upgrade add rpmsave extension to configuration 
files, which we should copy them back
example is /etc/httpd/conf/httpd.conf.rpmsave

also what is Pegasus ?
there is a lot of rpmsaved in  /var/lib/pegasus
example :
/var/lib/Pegasus/prev_repository_2007-08-30-1188481293.980554182.rpmsave

Thanks