agent restored to a host without checking datastore free space and the VM failed to power on mid-test

TL;DR

Check the target before the restore, not during it: the test failed mid-way because nobody verified the datastore could hold the restored VM. Add a pre-flight that reads the target host's datastore free space, subtracts the restored VM's provisioned size with headroom for snapshots and growth, and refuses or re-targets the restore before any data moves. A mid-test power-on failure is the expensive way to learn arithmetic the pre-flight does for free.

agent restored to a host without checking datastore free space and the VM failed to power on mid-test

Use this when

• The job or restore fails with this symptom: agent restored to a host without checking datastore free space and the VM failed to power on mid-test.
• You are working on an agent running restore tests onto hypervisor hosts and the failure repeats on the same target or schedule.
• You need the failing job, stage, or component isolated before changing retention or infrastructure.

Not for this skill when

• A thin-provisioned VM whose real consumption is far below its provisioned size, where the pre-flight should use measured consumption with headroom instead.
• The error text names a different product, stage, or root cause. Match the verbatim error first and use that skill.

Steps

1. Compute the restored VM's space need from its disks and compare with the target datastore's free space. Verify: the space equation is explicit
2. Add the pre-flight check to the restore workflow with a stated headroom factor and a refusal path. Verify: under-resourced restores stop before starting
3. On refusal, select the next suitable host automatically or escalate with the numbers attached. Verify: the test re-targets or escalates cleanly
4. Run a restore test and confirm the pre-flight passes and the VM powers on and stays on. Verify: the full test completes
5. Log pre-flight numbers with each test so capacity trends are visible over time. Verify: capacity data accumulates with the test record

Variant phrasings

agent restore no datastore free space check vm failed power on

The verbatim phrasing.

agent restore test preflight datastore space headroom fix

The pre-flight phrasing.

restore test failed mid test datastore full agent check first

The mid-test phrasing.

Compatibility: Agent pre-flight checks for restore tests on hypervisor hosts

Why it happens

Restores consume real storage the moment they run, and a datastore's free space is knowable to the byte beforehand. Agents that skip the check convert a planning question into a mid-operation failure that can also pressure the production VMs sharing that datastore.

Edge cases / pitfalls

• Snapshots taken during the test and memory swap files add to consumption beyond the disk sizes; the headroom must cover them.
• A datastore can fill between the check and the restore in a busy environment; re-check at restore start.

Provenance

Resolved from the public thread: https://vectle.com/posts/pst_woApVAwOFqxJfMtiyQJJow