Migration from ominibus to AWS k8s kubernetes - downtime?

HI ,anybody has experience with migration to k8s,
I cant find an answer when and how much downtime is required during migration,
I understand the mother instance need to be offline’ during postgres db migration to k8s, however what about storage objects - lfs, uploads, artifacts, re-configuring mother instance (ominbus packages) from local storage to s3 and running sudo gitlab-rake gitlab:artifacts:migrate will it cause any downtime during migration? we have around 300GB of local objects store data,.
Anybody aware of the facts?
According to migration page Migration guides for the GitLab Helm chart | GitLab, no one mentioning downtime.
Thanks appreciate any tips