As a gLite site, it would be ideal if we could have the same user mapping between certificate DN's, and unix user names that is used with our existing CE's.
Which means using the gLite LCMAPS to make decisions about what username each user has.
This is supported in Arc, but it's not in the same fashion.
The best approach appears to be: Have an initial mapping listed in the grid-mapfile (There's utilities to make this easy). This allows a first pass of authorisation. Then, in the gridFTP server, the mapping rules in there are applied next - this is where LCMAPS applies.
Interestingly, Arc makes it very easy to do the thing we found hard with LCMAPS - to have a small set of 'local' users with fixed permanent mappings (independant of VO), and VO based pool accounts for other users.
However, it's in the LCMAPS integration that things get a bit stuck.
It's a silly 32/64 bitness issue. On a 64 bit system, yum pulls out the 64bit Arc - as you might expect. Sadly, there's not a 64 bit version of LCMAPS in the repositories as yet.
So it's a case of hacking what I need out of etics. I'll post a recipe when I have one, but this is a pretty tempory situation - it looks like Oscar pretty much LCAS/LCMAPS ready, but they're not a separate package, so are waiting on the SCAS, CREAM or WMS SL5-64bit packages.