Debian operating system

I have an annoying problem on my server and google has been of no help. I have two drives mirrored for the OS through mdadm, and I recently replaced them with larger versions through the normal process of replacing one at a time and letting the new drive re-sync, then growing the raids in place. Everything is working as expected, with the exception of systemd... It is filling my logs with messages of timing out while trying to locate both of the old drives that no longer exist. Mdadm itself is perfectly happy with the new storage space and has reported no issues, and since this is a server I can't just blindly reboot it to get systemd to shut the hell up.

So what's the solution here? What can I do to make this error message go away? Thanks.

[Update] Thanks to everyone who made suggestions below, it looks like I finally found the solution in systemctl daemon-reload however there is a lot of other great info provided to help with troubleshooting. I'm still trying to learn the systemd stuff so this has all been greatly appreciated!