School me on server hard drive management. (Hot swap, SATA channels, LVM, backup, etc.)

[linux guy]

Mount point management.

Is there an easy was to know if a disk is mounted and act accordingly or
prevent data from being written to a mountpoint ?  Or to have the mount
point disappear when its not mounted ?

Example

Lets say I create a mount point /home/me/myth and that /home/me resides on
/dev/sda3.

Lets say that a disk labelled MYTH normally gets mounted there.  But lets
say that someone accidentally unplugs the MYTH disk and thus nothing is
mounted.  Lets say the myth backend starts recording and in the process
writing data to /home/me/myth.   If MYTH isn't mounted there, then that data
is going to get written to the mount point dir, ie /dev/sda3.

Is there any way to prevent that ?

Or how about this ?

Lets say I create a disk labelled IMAGE_BACKUP.   Lets say fstab mounts it
to /home/me/image_backup.  Lets say that I want cron to copy all the files
from /home/me/images to IMAGE_BACKUP at midnight when its mounted. How does
cron know that IMAGE_BACKUP is mounted to /home/me/image_backup so it
doesn't write data to /dev/sda3 ?  Ditto for rsync ?

Thanks
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