One account, several sites.
WHAT IS SHARED
Disk space Bandwidth CPU and memory limits Inode count PHP configuration, unless set per directory
WHAT THIS MEANS
One busy site affects the others.
One site hitting a resource limit affects all of them.
THE SYMPTOM
All sites slow at once, or all returning errors, when only one is busy.
HOW TO IDENTIFY THE CAUSE
Check which site is receiving traffic.
Raw access logs show requests per domain.
WHAT TO DO
Enable caching on all of them Address whichever is consuming most Consider separating a heavy site into its own account
THE SECURITY POINT
Sites in one account share a filesystem.
A compromise of one can reach the others.
WHEN TO SEPARATE
Client sites Anything you may hand over Anything where a compromise must be contained
