VERITAS Volume Manager 3.5 Administrator's Guide (September 2002)

Performance Monitoring

286 VERITAS Volume Manager Administrator’s Guide

If you do not specify any operands, vxtrace reports either all error trace data or all I/O

trace data on all virtual disk devices. With error trace data, you can select all accumulated

error trace data, wait for new error trace data, or both of these (this is the default action).

Selection canbe limited to a speciﬁc diskgroup, to speciﬁc VxVMkernel I/O object types,

or to particular named objects or devices.

For detailed information about how to use vxtrace, refer to the vxtrace(1M) manual

page.

Printing Volume Statistics

Use the vxstat command to access information about activity on volumes, plexes,

subdisks, and disks under VxVM control, and to print summary statistics to the standard

output. These statistics represent VxVM activity from the time the system initially booted

or from the last time the counters were reset to zero. If no VxVM object name is speciﬁed,

statistics from all volumes in the conﬁguration database are reported.

VxVM records the following I/O statistics:

◆ count of operations

◆ number of blocks transferred (one operation can involve more than one block)

◆ average operation time (which reﬂects the total time through the VxVM interface and

is not suitable for comparison against other statistics programs)

Thesestatistics are recordedforlogical I/O includingreads,writes, atomiccopies, veriﬁed

reads, veriﬁed writes, plex reads, and plex writes for each volume. As a result, one write

to a two-plex volume results in at least ﬁve operations: one for each plex, one for each

subdisk, and one for the volume. Also, one read that spans two subdisks shows at least

four reads—one read for each subdisk, one for the plex, and one for the volume.

VxVM also maintains other statistical data. For each plex, it records read and write

failures. For volumes, it records corrected read and write failures in addition to read and

write failures.

To reset the statistics information to zero, use the -r option. This can be done for all

objects or for only those objects that are speciﬁed. Resetting just prior to an operation

makes it possible to measure the impact of that particular operation.