The `tlast_change_over_time` function needs an interval wide enough to
consider the range of time we are intrested in. In this case, we want
to see if the BURP volume has been swapped in the last thirty days, so
the interval needs to be `30d`.
This alert counts how long its been since the number of "active" disks
in the RAID array on the BURP server has changed. The assumption is
that the number will typically be `1`, but it will be `2` when the
second disk synchronized before the swap occurs.
The way I am handling swapping out the BURP disk now is by using the
Linux MD RAID driver to manage a RAID 1 mirror array. The array
normally operates with one disk missing, as it is in the fireproof safe.
When it is time to swap the disks, I reattach the offline disk, let the
array resync, then disconnect and store the other disk.
This works considerably better than the previous method, as it does not
require BURP or the NFS server to be offline during the synchronization.
*mtrcs0.pyrocufflink.red* is a Raspberry Pi CM4 on a Waveshare
CM4-IO-BASE-B carrier board with a NVMe SSD. It runs a custom OS built
using Buildroot, and is not a member of the *pyrocufflink.blue* AD
domain.
*mtrcs0.p.r* hosts Victoria Metrics/`vmagent`, `vmalert`, AlertManager,
and Grafana. I've created a unique group and playbook for it,
*metricspi*, to manage all these applications together.
Dustin