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Using EMS HA Monitors > Chapter 2 Monitoring Disk Resources
Disk Monitor Reference |
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The EMS disk monitor reports information on the physical and logical volumes configured by LVM (Logical Volume Manager). Anything not configured through LVM is not monitored from the disk monitor. Monitored disk resources are:
Monitoring both the physical and logical volumes allows you to detect failures in both active and inactive volume groups and logical volumes and correct hardware problems that put node, application, or data availability at risk. Figure 2-1 “Disk Monitor Resource Class Hierarchy” shows the class hierarchy for the disk monitor. Items in boxes are resource instances that can be monitored. The pv_summary is a summary status of all physical volumes in a volume group. This status is based on the compiled results of SCSI inquiries to all physical volumes in a volume group; see “Physical Volume and Physical Volume Link Status”. If you
have configured package dependencies in MC/ServiceGuard, this resource
is used to determine package failover based on access to physical
disks. (See Chapter 1 for information on configuring MC/ServiceGuard
package dependencies.) If you are using the disk monitor with MC/ServiceGuard,
it is important that you configure physical volume groups (PVGs)
to give you the most accurate pv_summary for MC/ServiceGuard package
failover. See “Rules for Using the
EMS Disk Monitor The value in Table 2-1 “Interpreting Physical Volume Summary ” is used by the disk monitor to determine how conditions compare in logical operations. For example, you may create a request that alerts you when the condition is greater than or equal to SUSPECT. The numeric value allows you to tell which conditions qualify. Table 2-1 Interpreting Physical Volume Summary
The pv_summary resource may not be available for a given volume group in the following cases:
All checks for the validity of pv_summary are logged to both /etc/syslog and /etc/opt/resmon/log/api.log with the name of the local node and the identifier diskmond. Requests to monitor physical volumes and physical volume links give you status on the individual physical volumes and PV links in a volume group. In the case of most RAID arrays, this means the monitor can talk to the physical link to a logical unit number ( LUN) in the array. In the case of stand-alone disks, it means the monitor can talk to the disk itself. The pv_pvlink status is used to calculate pv_summary. Although it is somewhat redundant to use both, you might want to have more specific status sent by pv_summary, and only have status sent on pv_pvlinks if a device is DOWN. Pv_pvlinks and pv_summary supplement lv_summary by giving status on the accessibility of both active and inactive volume groups and logical volumes. To pinpoint a failure to a particular disk, bus, or I/O card, you need to use the disk monitor alerts in conjunction with standard troubleshooting methods: reading log files, inspecting the actual devices. The disk monitor uses the data in /etc/lvmtab to see what is available for monitoring, and /etc/lvmtab does not distinguish between physical volumes and physical volume links, so you need to do additional investigation to detect whether a disk, bus, or I/O card has failed. The value in Table 2-2 “Interpreting Physical Volume and Physical Volume Link Status” is used by the disk monitor to determine how conditions compare in logical operations. For example, you may create a request that alerts you when the condition is greater than or equal to BUSY. The numeric value allows you to tell which conditions qualify. Table 2-2 Interpreting Physical Volume and Physical Volume Link Status
When configuring requests from the SAM interface, a wildcard (*) may be used in place of deviceName to monitor all physical volumes and physical volume links in a volume group. The logical volume summary tells you how accessible the data is in all logical volumes in an active volume group. Sometimes the physical connection may be working, but the application cannot read or write data on the disk. The disk monitor determines I/O activity by querying LVM, and marks a logical volume as DOWN if a portion of its data is unavailable.
The values in Table 2-3 “Interpreting Logical Volume Summary” are used by the disk monitor to determine how conditions compare in logical operations. For example, you may create a request that alerts you when the condition is greater than or equal to INACTIVE_DOWN. Table 2-3 Interpreting Logical Volume Summary
Logical volume status gives you status on each logical volume in a volume group. While the lv_summary tells whether data in a volume group is available, the lv/status/lvName will tell you whether specific logical volumes have failed. The value in Table 2-4 “Interpreting Logical Volume Status” is used by the disk monitor to determine how conditions compare in logical operations. For example, you may create a request that alerts you when the condition is greater than or equal to INACTIVE. The numeric value allows you to tell which conditions qualify. Table 2-4 Interpreting Logical Volume Status
When configuring requests from the SAM interface, a wildcard (*) may be used in place of lvName to monitor all logical volumes in a volume group. If you split off mirrors from your mirrored configuration, you will see new logical volume resource instances when the split mirror is created. The logical volume number of copies is most useful to monitor in a mirrored disk configuration. It tells you how many copies of the data are available. MirrorDisk/UX supports up to 3-way mirroring, so there can be from 0 to 3 copies (see Table 2-5 “Interpreting Logical Volume Copies”.) In a RAID configuration that is not mirrored using LVM, the only possible number is 0 or 1; either the data is accessible or it isn't. Note that when you configure mirroring in LVM, it lists 0 mirrors to mean you have one copy of the data. Likewise, 2 mirrors mean you have 3 copies of the data (one original plus 2 mirrors). The disk monitor is monitoring all copies of data, and therefore counts the "original" as part of the total number of copies. Table 2-5 Interpreting Logical Volume Copies
When configuring requests from the SAM interface, a wildcard (*) may be used in place of lvName to request status for all logical volumes in a volume group. If you split off mirrors from your mirrored configuration, you will see the number of copies reduced by 1 when the split mirror is created. |
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