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190 IBM Certification Study Guide AIX HACMP
After setting the cluster’s security settings to enhanced for all these nodes,
you can verify that it is working as expected, for example, by running clverify,
which goes out to the nodes and checks the consistency of files.
9.3 VSDs - RVSDs
VSDs (Virtual Shared Disks) and RVSDs (Recoverable Virtual Shared Disks)
are SP-specific facilities that you are likely to use in an HACMP environment.
9.3.1 Virtual Shared Disk (VSDs)
Virtual Shared Disk (VSD) allows data in logical volumes on disks physically
connected to one node to be transparently accessed by other nodes.
Importantly, VSD supports only raw logical volumes, not file systems. The
VSD facility is included in the ssp.csd.vsd fileset of PSSP.
IBM developed VSD to enable Oracle’s parallel database on the SP. Oracle’s
database architecture is strongly centralized. Any processing element, or
node, must be able to “see” the entire database. In the case of the parallel
implementation of Oracle, all nodes must have access to all disks of the
database, regardless of where those disks are physically attached.
Figure 17. VSD Architecture
Node X
Application
VSD
LVM IP
Cache
LVMIP
Disk DDNet DD
Node Y
Application
VSD
Cache
Disk DD Net DD
lv_X
lv_Y
IP Network (SP Switch)