Why does iostat and sar -d sometimes output incorrect results?
Issue
- On machines with heavy io loads, the output of sar -d is faulty, displaying some very large numbers.
- Using nr_requests for testing with high values (50,000+), iostat displays incorrect results fairly frequently.
- Example of "bad" sar -d output:
09:20:01 PM DEV tps rd_sec/s wr_sec/s avgrq-sz avgqu-sz await svctm %util
09:25:01 PM sdb1 0.52 0.03 5.52 10.60 0.00 1.27 1.02 0.05
09:30:01 PM sdb1 0.54 0.19 5.57 10.73 0.00 1.74 1.30 0.07
09:35:01 PM sdb1 33.64 259.94 47.26 9.13 0.04 1.17 0.29 0.96
09:40:01 PM sdb1 2202.02 6257.93 24939.09 14.17 2078.79 943.69 0.30 66.15
09:45:01 PM sdb1 3051.57 0.27 36532.41 11.97 1989.30 638.13 0.28 86.88
09:50:01 PM sdb1 2986.02 0.05 34704.99 11.62 3355.91 1137.22 0.28 84.49
09:55:01 PM sdb1 3284.08 0.21 32884.03 10.01 4556.98 1386.29 0.27 88.31
10:00:01 PM sdb1 3260.33 0.19 31497.61 9.66 61474802782539.38 18855397092136.58 0.27 87.60
10:05:01 PM sdb1 3373.57 0.08 32028.26 9.49 6069.53 1799.10 0.27 89.86
Environment
- Red Hat Enterprise Linux 5
- Sysstat 7.0.2 (reproduced in upstream version 10.0.2)
- Red Hat Enterprise Linux 6
- Sysstat version below 9.0.4-20
Subscriber exclusive content
A Red Hat subscription provides unlimited access to our knowledgebase of over 48,000 articles and solutions.
Close
Welcome! Check out the Getting Started with Red Hat page for quick tours and guides for common tasks.