Erroneous 'avgqu-sz' and 'await' values reported in SAR's disk i/o output in Red Hat Enterprise Linux 6
Issue
A Red Hat Enterprise Linux (RHEL) 6 guest running in a Red Hat Enterprise Virtualization (RHEV) 3.0 environment is randomly stalling during the day. Looking at sar data, there are disk I/O values which appear to be invalid.
Sample output from 'sar -d' shows such values in the 'avgqu-sz' and 'await' fields;
00:00:01 DEV tps rd_sec/s wr_sec/s avgrq-sz avgqu-sz await svctm %util
10:40:01 PM dev253-1 3950.86 0.00 32185.57 8.15 491.45 124.39 0.06 23.49
10:50:01 PM dev253-1 3943.85 0.00 32077.66 8.13 2234.90 566.68 0.11 44.15
11:00:01 PM dev253-1 3851.51 0.00 31316.39 8.13 1910.65 496.08 0.10 36.65
11:10:01 PM dev253-1 2778.78 0.00 22765.88 8.19 30599227121898.37 11011745589412.31 0.12 33.95
Environment
- Red Hat Enterprise Virtualization (RHEV) 3.0
- Red Hat Enterprise Linux (RHEL) 6
- sysstat-9.0.4-18
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