Ok; I’ve managed to work out a solution. It’s not pretty at all, but it’s working:
rt-shredder can’t handle the volume of data to delete. Since rt-shredder can’t complete execution, nothing is getting deleted from the database.
So; I’m using PuTTY to log the output from what rt-shredder claims its doing. Once it dies, or I stop it, I then upload the log file to my RT server. I then run a second Perl script that parses the files line by line and executes rt-shredder one a single object at a time. I went from 9.7 million attachments down to 9.56. So now; I just have to keep this up until I can get the counts down low enough to run the rest of the repair tools on the database (rt-validator, etc).