Comment 0 for bug 1888345

We are migrating our servers to Ubuntu Focal and we have noticed that our custom charts show unreal values for disk usage.

The issue only happens when you choose the JSON output flag. We have already open an issue on github and the maintainer confirmed the bug. https://github.com/sysstat/sysstat/issues/264

I have checked that on version 12.3.4 it's solved, but Ubuntu Focal uses 12.2.0 and this version is affected by the issue.

This is the commit with the fix: https://github.com/sysstat/sysstat/commit/404eee1417dad8abe6ef49ea6e1469fe6cfdddbe

These are the steps to reproduce the issue. We use the command iostat /dev/sdb -dmx 1 -o JSON in one terminal and the same command whithout -o JSON in another one, and you'll see that all the values match except wMB/s, I attach three examples below:

"disk": [
 {"disk_device": "nvme0n1", "r/s": 0.00, "w/s": 31.00, "d/s": 0.00, "rMB/s": 0.00, "wMB/s": 248.00, "dMB/s": 0.00, "rrqm/s": 0.00, "wrqm/s": 0.00, "drqm/s": 0.00, "rrqm": 0.00, "wrqm": 0.00, "drqm": 0.00, "r_await": 0.00, "w_await": 1.87, "d_await": 0.00, "rareq-sz": 0.00, "wareq-sz": 4.00, "dareq-sz": 0.00, "aqu-sz": 0.00, "util": 0.80}
 ]

Device r/s rMB/s rrqm/s %rrqm r_await rareq-sz w/s wMB/s wrqm/s %wrqm w_await wareq-sz d/s dMB/s drqm/s %drqm d_await dareq-sz aqu-sz %util
nvme0n1 0,00 0,00 0,00 0,00 0,00 0,00 31,00 0,12 0,00 0,00 1,87 4,00 0,00 0,00 0,00 0,00 0,00 0,00 0,00 0,80

"disk": [
 {"disk_device": "sdc", "r/s": 0.00, "w/s": 2.00, "d/s": 0.00, "rMB/s": 0.00, "wMB/s": 24.00, "dMB/s": 0.00, "rrqm/s": 0.00, "wrqm/s": 1.00, "drqm/s": 0.00, "rrqm": 0.00, "wrqm": 33.33, "drqm": 0.00, "r_await": 0.00, "w_await": 2.00, "d_await": 0.00, "rareq-sz": 0.00, "wareq-sz": 6.00, "dareq-sz": 0.00, "aqu-sz": 0.00, "util": 0.40}
 ]

Device r/s rMB/s rrqm/s %rrqm r_await rareq-sz w/s wMB/s wrqm/s %wrqm w_await wareq-sz d/s dMB/s drqm/s %drqm d_await dareq-sz aqu-sz %util
sdc 0.00 0.00 0.00 0.00 0.00 0.00 2.00 0.01 1.00 33.33 2.00 6.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.40

"disk": [
 {"disk_device": "sdb", "r/s": 0.00, "w/s": 35.00, "d/s": 0.00, "rMB/s": 0.00, "wMB/s": 280.00, "dMB/s": 0.00, "rrqm/s": 0.00, "wrqm/s": 0.00, "drqm/s": 0.00, "rrqm": 0.00, "wrqm": 0.00, "drqm": 0.00, "r_await": 0.00, "w_await": 0.11, "d_await": 0.00, "rareq-sz": 0.00, "wareq-sz": 4.00, "dareq-sz": 0.00, "aqu-sz": 0.00, "util": 0.40}
 ]

Device r/s rMB/s rrqm/s %rrqm r_await rareq-sz w/s wMB/s wrqm/s %wrqm w_await wareq-sz d/s dMB/s drqm/s %drqm d_await dareq-sz aqu-sz %util
sdb 0.00 0.00 0.00 0.00 0.00 0.00 35.00 0.14 0.00 0.00 0.11 4.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.40