Hello Peter,
Thanks for the answer. I figured it out when reading this topic : http://www.windows-noob.com/forums/index.php?/topic/11444-best-way-for-cm12-side-by-side-migration/.
Ideed, your proposal seems OK to me : Build new R2 site, upgrade existing SP1 site to R2 then migrate it side by side. I'm going to study this scenario.
Otherwise, is it possible to do a sort of "manual" migration ? I'm asking because I think retrieving the active software update groups and deployments should be the biggest part as I occasionally create programs and packages and I don't use advanced features such as OSD, Asset Intelligence, or baselines. May be I could :
Keep the old site in SP1
Install new site in R2
Enable SUP and EP roles.
Re-create software update groups and download approved updates.
Re-create ADR to allow defintions updates.
Remove old site boudaries and create ones on the new one to move client computers.
Uninstall old site.
Decommission old server.