Deleting local disks may consume all available space on a disk, crashing omicron services

[wfchandler]

We've observed this happen on dogfood and on a customer rack running v18.1. In the latter case, the customer was creating local disks of various sizes to determine the largest size available.

[leftwo]

In storage huddle 3/11/26 we discussed this, and the idea/plan of the following.

When a local storage volume is deleted, the first step will be to remove the quota and reservation on the parent dataset.
Next, we do the delete of the raw zvol.
Finally, delete the parent dataset.

In the storage huddle 3/13/26, George tested this path and verified it did not encounter the out of space issue.