Support of Oracle RAC ASM with SGeRAC, January 2008

HP Availability Clusters Solutions Lab 1/25/2008 Page 8
The idea is that ASM provides the mirroring, striping, slicing and dicing functionality as needed and
SLVM supplies the multipathing functionality not provided by ASM. Figure 4 indicates this 1-1
mapping between SLVM PVs and LVs used as ASM disk group members.
Further, the default retry behavior of SLVM could result in an I/O operation on an SLVM LV taking an
indefinitely long period of time. This behavior could impede ASM retry and rebalance capabilities;
hence a finite timeout must be configured for each SLVM LV. For example, the timeout could be
configured to the value (total number of physical paths to the PV * PV timeout), providing enough time
for SLVM to try all available paths, if needed.
4
The PVs used in an ASM disk group can be organized into SLVM volume groups as desired by the
customer. In the example shown in Figure 4, for each ASM disk group, the PVs corresponding to its
members are organized into a separate SLVM volume group.
Figure 4. 1-1 mapping between SLVM logical and physical volumes for ASM configuration
4
If the LVM patch PHKL_36745 (or equivalent) is installed in the cluster, a timeout equal to (2* PV timeout) will suffice to try all paths.
Physical
V
olumes
DB Instances
A
SM Instanc
e
SLVM Volume
Groups
Lo
g
ical
V
olumes
ASM Disk
Groups
DG1
DGn
V
G1
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Disk Group
Members