So far, I have been unsuccessful in using xtrabackup to do the migration.
version not supported – mysql side … version of xtrabackup had dropped support for 5.1.56
backup is corrupt – on maria side - md5sums matched
failed to start – from maria after extracting the backup (nothing informative in the maria logs, no errors popped by xtrabackup)
So has anyone successfully done such a migration or have thoughts on version(s) of xtrabackup to use ?