Splitting the dCache head node

As your dCache installation grows, you may find it necessary to split the services onto separate nodes to reduce the load (which can cause timeouts between components of dCache).

PNFS

PNFS particularly vulnerable to this effect which often leads to problems like files being left orphaned (on disk, but not in namespace) or being owned by root:root (I think this is one source that causes this problem). There is some documentation out there about splitting off the PNFS database and PnfsManager cell of dCache:

• http://trac.dcache.org/trac.cgi/wiki/manuals/FAQ#IwanttomigratePNFStoadifferenthost
• http://www-pnfs.desy.de/movedb.html
• http://www.dcache.org/archive/user-forum/1055.html

Basically all you need to do is dump the PNFS database (you don't need the SRM stuff, but you can take it if you are paranoid) and move it to the new host. Starting up PNFS should then allow you to mount the migrated /pnfs filesystem on the doors and SRM node. Make sure that the other dCache components know where the new PNFS node resides.

There should not be any problems in performing this process. You should ensure that you use the same version of postgres on both hosts.

dump existing DB:       $ pg_dumpall > db.out
restore on new host:    $ psql -f db.out postgres

You should also make sure that the /var/lib/pgsql/data/pg_hba.conf files are the same on both servers (or sufficiently configured that all existing users of the DB can still access it).