Experience migrating from clearcase?

[Steve Gardell <sg...@iperia.com>]

We are looking to migrate a long-standing (several years) development
activity from clearcase to subversion. A web-search demonstrates that
I am not the first to look at this; all the same I struggle a bit to
find
the right model.
 
In the ideal world, I would reflect my years of clearcase history with
the
many branches and tags into Subversion. At least conceptually this
seems quite doable.
 
To have this be really useful it seems that I would need to order all 
checkins to clearcase over all files since time t (some arbitrary
cut-off in the past)
and then update subversion in that order. Thus I would be able to
reproduce the state of my clearcase vob at any point in time in the past
-
allowing me to build old versions... The alternative model of handling
all of the changes to each file in turn doesn't really seem to work,
does it?
 
So I am left wondering if it is really worth while. Maybe better to just
cut-n-run
and then lock the clearcase vobs to "read-only" for the historically 
minded?
 
What are others doing when they migrate from file-versioned systems to
repository-versioned systems?
 
Thanks!