diskio module: only relies on physical block devices, not working with LUKS encrypted devices
Strange, the data should be kept on update. Could you send the log file (probably /var/webmin/modules/sysstats/webminstats.debug) and some infomations on your host (linux distribution,and version), webmin version ...
Each module contains a Changelog file, which will be installed. For example on a debian, the changelog for the load module is /usr/share/webmin/sysstats/modules/load/Changelog.
diskio module: only relies on physical block devices, not working with LUKS encrypted devices
I have released a new version of diskio module (1.8) on https://sourceforge.net/projects/webminstats/files/updates/2.23/ which includes device mapper devices
Extend record time
I keep the idea for the customisation in my todo list Another simpler way may be to only add records in the last rra, which is possible with the rrdresize command (https://oss.oetiker.ch/rrdtool/doc/rrdresize.en.html)
mem and process modules: no data since Debian 13 / start from scratch