It's a bit glib, because data varies so much, but my personal favourite data migration tool is Perl. I've migrated a lot of "stuff" from one place to another,

It's a bit glib, because data varies so much, but my personal favourite data migration tool is Perl. I've migrated a lot of "stuff" from one place to another, from filesystems, to databases, to backups, and there is usually some perl running in the background. Of course the scale is very different. The biggest thing I've personally migrated was in the low Tb of data. Certainly nothing so large/necessary as banking stuff.