Where RAC database stores data

Storage Options for RAC

1--CFS (Cluster File System) – Easy to manage but only available on some platforms.  Does not address striping and mirroring.
2--RAW – Available on all platforms but difficult to manage. Does not address striping and mirroring.
3--NFS – Easy to manage but only available on some platforms.  Does not address striping and mirroring.
4--ASM (Automatic Storage Management) – Easy to manage, available on ALL platforms, and DOES address striping and mirroring.

CFS (Cluster Filesystems)

The idea of CFS is to basically share file filesystems between nodes.
Easy to manage since you are dealing with regular files.
CFS is configured on shared storage.  Each node must have access to the storage in which the CFS is mounted.
NOT available on all platforms.  Supported CFS solutions currently:
OCFS on Linux and Windows (Oracle)
DBE/AC CFS (Veritas)
GPFS (AIX)
Tru64 CFS (HP Tru64)
Solaris QFS

RAW (character devices)

Hard to manage since you are dealing with character devices and not regular files.
Adding and resizing datafiles is not trivial.
On some operating systems volume groups need to deactivated before LVs can be manipulated or added.

NFS (Network Filesystem)

NOT available on all platforms.  Supported NFS solutions currently:
Network Appliance
Redhat Linux
Fujitsu Primecluster
Solaris Suncluster

ASM

Stripes files rather than logical volumes.
Enables online disk reconfiguration and dynamic rebalancing.
Provides adjustable re balancing speed.
Provides redundancy on a file basis.
Supports only Oracle files.
Is cluster aware.
Is automatically installed as part of the base code set