Using High Availability Monitors (June 2007)

Monitoring Disk Resources
Rules for Using the HA Disk Monitor with ServiceGuard
Chapter 2 39
These rules apply when creating a PVG. If the rules are not followed,
pv_summary will not be available for monitoring:
• If PVGs are used, all physical volumes in a volume group must be in
a PVG.
• All PVGs in a volume group must have the same number of physical
volumes.
Table 2-7 is a summary of how pv_summary is calculated where
• n is the number of paths for the volume group in /etc/lvmtab
(physical volumes, paths, or LUNs).
• p is the number of PVGs (physical volume groups) in the volume
group
• x is the number of paths currently available from a SCSI inquiry
To give pv_summary the most accurate picture of data availability, you
need to use PVGs to define your physical volumes as separate access
points to data. Mirroring should be PVG-strict. Arrays should have PV
links, with redundant links in a separate PVG. Note that if you do not
Table 2-7 pv_summary Calculations
Case Conclusion State
x = n All physical volumes and all data
are available.
UP
n>x>=n - (p-1) All data is available. PVG_UP
n/p <= x <= n-(p-1)
If there are PVGs, and one PVG
has all paths, then all data is
available.
PVG_UP
If there are PVGs, and none of the
PVGs has all paths, then the HA
Disk Monitor cannot determine if
all data is available.
SUSPECT
x < n/p Some data is missing.
DOWN
x=0 No data or physical volumes are
available.