Percona Server can also fail to start if it starts before the network or local mount of datadir is mounted

Similar to PXC-3637, in PXC this was resolved after adding these changes in the service file:

[Unit]
Description=Percona XtraDB Cluster
After=network.target syslog.target local-fs.target remote-fs.target
Require=local-fs.target remote-fs.target

This ensures that PXC can only start when local and remote mounts are mounted.

However, in Percona Server, this requirement is not set:

[Unit]
Description=MySQL Server
Documentation=man:mysqld(8)
Documentation=http://dev.mysql.com/doc/refman/en/using-systemd.html
After=network.target
After=syslog.target

Here Percona Server can start for as long as syslog and network are up and running which can be a problem if the local or network mounts that contain the data directory is not mounted yet.