Support of Oracle RAC ASM with SGeRAC, January 2008

HP Availability Clusters Solutions Lab 1/25/2008 Page 12
Maximum SGeRAC cluster size for
ASM configurations is 16
SGeRAC Toolkit
3
framework based
on Multi-Node Package (MNP)
/Simple Package Dependency to
manage ASM configurations on
SGeRAC up to a maximum cluster
size of 16
Raw disks/disk array LUs as ASM
Disk Group Members.
ASM over SLVM
SGeRAC support for ASM-over-SLVM continues in HPUX 11i v3. SGeRAC 11.17.01 or later is
required for ASM-over-SLVM configurations on HP-UX 11i v3.
The advantages of the "ASM-over-SLVM" configuration are as follows:
• ASM-over-SLVM ensures that the HP-UX devices used for disk group members will have the
same names (the names of logical volumes in SLVM volume groups) on all nodes, easing
ASM configuration.
• ASM-over-SLVM protects ASM data against inadvertent overwrites from nodes
inside/outside the cluster. If the ASM disk group members are raw disks, there is no
protection currently preventing these disks from being incorporated into VxVM volume/disk
groups.
The disadvantages of the ASM-over-SLVM configuration are as follows:
• Additional configuration and management tasks are imposed by the extra layer of volume
management (administration of volume groups, logical volumes, physical volumes)
• There is a small performance impact from the extra layer of volume management
• SLVM has some restrictions in the area of online reconfiguration, the impact of which will
be examined later in this document
Configuring SLVM Volume Groups for ASM Disk Groups
We would like the logical volumes presented to ASM to resemble raw disks, as far as possible.
Hence, each SLVM logical volume (LV) used as a member of an ASM disk group is required to be laid
out to occupy the usable space, in contiguous fashion, of exactly one single physical volume (PV). This
implies that the LV
• should be contiguous,
• should not be striped or mirrored,
• should not span multiple PVs
• and should not share a PV with other LVs.