first sysstat/sar log doesn't include block device activity

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Environment

SUSE Linux Enterprise Server 12 Service Pack 5 (SLES 12 SP5)

SUSE Linux Enterprise Server 12 Service Pack 4 (SLES 12 SP4)

SUSE Linux Enterprise Server 12 Service Pack 3 (SLES 12 SP3)
SUSE Linux Enterprise Server 15

Situation

When the sysstat service is enabled for the first time or after reboot, the "Report activity for each block device" will be missing until after midnight.

The reported output is:

# sar -d
Requested activities not available in file /var/log/sa/sa<date>

instead:

# sar -d
Linux <kernelversion>-default (<hostname>)        <date>      <architecture>       (X CPU)

<time> PM LINUX RESTART      (X CPU)

<time>   PM       DEV       tps     rkB/s     wkB/s   areq-sz    aqu-sz     await     svctm     %util
<time>   PM    dev8-0      0.09      0.00      0.85      8.91      0.00      0.49      0.49      0.00
<time>   PM   dev11-0      0.00      0.00      0.00      0.00      0.00      0.00      0.00      0.00
Average:       dev8-0      0.09      0.00      0.85      8.91      0.00      0.49      0.49      0.00
Average:      dev11-0      0.00      0.00      0.00      0.00      0.00      0.00      0.00      0.00

Resolution

In /etc/sysstat/systat changing the option SADC_OPTIONS=" " to SADC_OPTIONS='-S ALL ' resolves it.

The following SLES/SP updates include the patch, applying the change of this option automatically and making it default:

The SLES12 SP4 sysstat-12.0.2-10.30.1, released November 2019

The SLES12 SP5 sysstat-12.0.2-10.27.1, released December 2019

The SLE15 GA/SP1 sysstat-12.0.2-3.18.1, released November 2019

Cause

When the sysstat.service is started by systemd it is run with the "-boot" option:

[Service]
Type=oneshot
ExecStart=/usr/lib64/sa/sa1 --boot
ExecStart=/bin/ln -fs /etc/sysstat/sysstat.cron /etc/cron.d/sysstat
[...]

The sa<date> file is written to /var/log/sa/. It uses the default options and doesn't gather any extended data.

Once this sar log file is created no new fields can be added.

When cron starts data collection every 10 minutes with the option "-S ALL", no new data can be added to the file.

So for the first data collection only default options are used.

After midnight, when the file is rolled over and this time cron generates the new file with: "-S ALL", the block device activity will be written.

Disclaimer

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