BUG REPORT: check_drive_io not seeing C: drive in Windows

[HerrKartoffelKopf]

When using the new check_drive_io on Windows systems, I'm seeing that it doesn't appear to be picking up the C: drive at all, but does detect any other disks such as E: or F:.

To Reproduce
From Nagios, run the command check_drive_io against a server that has version 0.42. I've run a few examples here. Firstly, against a VM that only has a single drive:

./check_nrpe -H 10.1.1.250 -c check_drive_io
OK -

And, on a VM that has 3 x drives installed we see more of what we would expect, minus the C: drive:

./check_nrpe -H 10.1.1.99 -c check_drive_io
OK - E (%(label)) >%(write_bytes_rate_humanized) <%(read_bytes_rate_humanized) 0.0%, F (%(label)) >%(write_bytes_rate_humanized) <%(read_bytes_rate_humanized) 0.0% |'E_read_count'=39930080c;;;0 'E_read_bytes'=3194782899200c;;;0 'E_read_time'=8569655556.983701ms;;;0 'E_write_count'=9850045c;;;0 'E_write_bytes'=532356810240c;;;0 'E_write_time'=3815578629.0907ms;;;0 'E_utilization'=0%;95;;0 'E_queue_depth'=0;;;0 'F_read_count'=653906c;;;0 'F_read_bytes'=671960099840c;;;0 'F_read_time'=5901588.2482ms;;;0 'F_write_count'=19916253c;;;0 'F_write_bytes'=1851469408256c;;;0 'F_write_time'=48563676.6862ms;;;0 'F_utilization'=0%;95;;0 'F_queue_depth'=0;;;0

Expected behavior
The C: drive should be expected in results when not specifying any arguments to filter the drive list.

Software (please complete the following information):
I've managed to test this with Windows Server 2019 and 2022.

[inqrphl]

Hi, would it be possible for you to run the snclient executable directly on the VM to get its output? Using remote checker tools like check_nrpe wont return the full logs of the snclient.

Terminal 1 on the VM with 3 drives installed, start the snclient in server mode

PS C:\Users\vagrant\repositories\snclient> ./snclient -vvv --logfile stdout

You might be getting something like this if your drive does not support the IOCTL call. But it is weird that your E and F drive works when C does not. Are they the same type of drive?

[2026-02-17 09:11:30.774][Trace][pid:952][task_check_system_windows:246] Logical drive Z, got an error from Ioctl IOCTL_STORAGE_GET_DEVICE_NUMBER. Likely has no physical device e.g VirtioFS/Network. 
Err: The volume does not contain a recognized file system.
Please make sure that all required file system drivers are loaded and that the volume is not corrupted.

Later on you should see the counters being initialized:

[2026-02-17 09:11:30.985][Trace][pid:952][snclient:1526] creating counter disk_C.write_bytes (buffer: 15m0s)
[2026-02-17 09:11:30.985][Trace][pid:952][snclient:1526] creating counter disk_C.write_count (buffer: 15m0s)
[2026-02-17 09:11:30.985][Trace][pid:952][snclient:1526] creating counter disk_C.read_bytes (buffer: 15m0s)
[2026-02-17 09:11:30.985][Trace][pid:952][snclient:1526] creating counter disk_C.read_count (buffer: 15m0s)
[2026-02-17 09:11:30.986][Trace][pid:952][snclient:1526] creating counter disk_C.idle_time (buffer: 15m0s)
[2026-02-17 09:11:30.986][Trace][pid:952][snclient:1526] creating counter disk_C.query_time (buffer: 15m0s)

After starting the snclient on the VM, wait around a minute and send your query on a separate terminal:

./check_nrpe -H 10.1.1.99 -c check_drive_io lookback=30

If your C disk counters are not being initialized, can you tell me more about the VM? Are you using KVM / VirtualBox / VMWare or Windows Hyper-V? How does the drive look on Windows device manager?

We tested this check on a real machine with physical drives and a KVM virtio drive, and it worked.

    <disk type="file" device="disk">
      <driver name="qemu" type="qcow2"/>
      <source file="/var/lib/libvirt/images/windows-10-enterprise-x64-eval_default.img"/>
      <target dev="vda" bus="virtio"/>
      <alias name="ua-box-volume-0"/>
      <address type="pci" domain="0x0000" bus="0x00" slot="0x05" function="0x0"/>
    </disk>

Thanks