Support of Oracle RAC ASM with SGeRAC, January 2008

HP Availability Clusters Solutions Lab 1/25/2008 Page 3
Figure 1. Oracle database storage hierarchy without and with ASM
Please note that the 'with ASM' stack shows raw disks/disk array logical units (LUs) being used by
ASM. This is consistent with the Oracle perspective of ASM playing the role of the volume manager
and file system in managing Oracle data.
Single Node (Non-Clustered) ASM Environment
ASM on HP-UX is a user-space storage manager (although ASM defines a kernel library interface that
can provide extended ASM functionality, this library is not provided on HP-UX).
Figure 2 shows the ASM environment within a single non-clustered node. Typically there is only one
ASM instance per node (irrespective of whether it is part of a high-availability cluster or not). It
provides services to potentially multiple Oracle database instances running on that node and
configured to use ASM-managed storage.
The ASM instance is responsible for
• creating/modifying/destroying ASM disk groups and the database files contained in them,
• managing the mirroring and striping of db files in ASM disk groups, including rebalancing
as needed, and
• providing database file layout information to client database instances.
In structure, the ASM instance resembles a database instance.
W
ithout ASM
W
ith ASM
Tables
Tablespaces
Files
File Systems
Lo
g
ical Volumes
V
olume Groups
Disks/Disk Array
Logical Units
0111000
00100…
..
0111000
00100…
..
(S)LVM,
V
xVM,
CVM
V
xFS,
CFS,..
Files and Disk Groups
Managed by ASM,
displayed via Oracle
utilities