we did nearly the same procedure the last time we switched from an old Qpopper maschine to a new Qpopper maschine. The last time we had not so much users (maybe 16000), not so much data (round about 20Gigs) and there was no need of conversion. This time we have new DNS-Names, new environment (Dovecot) and so on.
That should not pose any real problems :)
So David, may I ask you how long did it take to convert the data?
We used a cross-link cable between the two machines to transfer the data over their gigabit link. Both systems had three 10k rpm SCSI disks in hardware RAID 5 which pushed data at around 20 mb/s. That took around 20 minutes.
Now for the migration script, that took about 1:30 hours to run on a single Intel Xeon 2.80GHz.
Cheers,
David
David Robillard UNIX systems administrator & Oracle DBA CISSP, RHCE & Sun Certified Security Administrator Montreal: +1 514 966 0122