Two days ago I had started this upgrade, now it is finished and I
just wanted to share my notes.  I am speaking about the MySQL
flavor for the DPM head, because we're running this configuration.

1. Such an upgrade can be done without OS reinstallation by
   using YUM, YAIM and some hand work; you can separately upgrade
   the head and the pools: in our case the head was upgraded first
   and it coexisted with the gLite 3.2 DPM pools for a while without
   any visible problems.

2. One thing is that the passwords for MySQL DPM and DPNS databases
   are now limited to 32 characters; while it won't be the problem
   for most sites, we had 36 characters, so I was beaten by this
   issue, because the log message wasn't clear.  But DPM developers
   were quick when I had explained the problem to them and there is
   a ticket, https://svnweb.cern.ch/trac/lcgdm/ticket/433

3. Just doing 'yum install -y emi-DPM_disk' on the pool nodes
   won't work, because
   a) you will need to remove packages vdt_globus_data_server,
      vdt_globus_essentials and lcg-service-proxy;
   b) and remove the remains of /opt/globus (you can cross-check
      that after doing item "a" there is only one auto-generated
      file left in that directory ('find /opt/globus -type f' will
      help here.
   The problem is that the startup scripts for dpm-gsiftp are
   written in such a way that they will pick up /opt/globus
   as the GLOBUS_LOCATION if that directory exists.  And this
   won't work, because DPM plugins are in /usr.

4. After doing 'yum install -y emi-DPM_<foo>' on the head and
   nodes I had spotted that not every package was updated, so
   additional 'yum upgrade' was needed (and YAIM was invoked
   after it to catch any mis-configurations after package
   upgrades).

I hadn't seen any troubles apart from these ones and now our DPM
is alive and kicking (600 Tb of space for CMS and ATLAS).

So, thanks to the DPM team for a mostly smooth upgrade for the
major transition from gLite to UMD-1 at our site.

Any suggestions and/or corrections are welcome.
-- 
Eygene Ryabinkin, National Research Centre "Kurchatov Institute"

Always code as if the guy who ends up maintaining your code will be
a violent psychopath who knows where you live.