1 second delay in capturing the sar data.

Solution Verified - Updated -

Issue

  • Collecting 1 second sar data, with the cron job: 
/usr/lib64/sa/sa1 -S INT 1 50400

For most statistics this reports is correct. However Some busy network interfaces running at 1000/full, and the sar data shows all zero's, every other second...

Example:

$ sar -n DEV | grep eth7
06:00:19 AM      eth7     26.00      0.00      1.52      0.00      0.00      0.00     26.00
06:00:20 AM      eth7      0.00      0.00      0.00      0.00      0.00      0.00      0.00
06:00:21 AM      eth7     26.00      0.00      1.52      0.00      0.00      0.00     26.00
06:00:22 AM      eth7      0.00      0.00      0.00      0.00      0.00      0.00      0.00

Presumption is, this is just a "feature" of sar and that it cannot "handle" such throughput of data. Is this correct ?

Environment

  • Red Hat Enterprise Linux 5.6
  • Kernel-2.6.18-238.9.1.el5
  • sysstat-9.0.4-1.x86_64
  • igb Drivers
  • e1000e Drivers

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