From here,
Oracle ASM provides several advantages over conventional file systems and storage managers, including the following:
- Rebalances data automatically after storage configuration changes
What kind of configuration changes are we talking about here? In a database, what kind of configuration changes happen?
"What kind of configuration changes are we talking about here?"
Adding new hard drives, reconfiguring the SAN, replacing DAS with NAS or SAN.
The point of ASM is to shield the database from the physical directory structure. Tablespaces are logical structures which provide one layer of indirection, but they are still tied to actual OS files. ASM uses another logical structure, the disk group, which operates at a lower level. It manages the allocation of actual OS storage resource to the disk groups.