running on mysql/0 unit
$time timeout 120m ionice -c3 mysqldump -u root -p*censored* --opt --all-databases --skip-lock-tables |xz -1 > xxx
mysqldump: [Warning] Using a password on the command line interface can be insecure.

real	0m16.557s
user	0m19.180s
sys	0m1.672s

running from juju
$ time juju run --unit=mysql/0 'timeout 120m ionice -c3 mysqldump -u root -p*censored* --opt --all-databases --skip-lock-tables|xz -1' > xxx
action terminated
real	0m28.429s
user	0m0.048s
sys	0m0.164s