1# VM Quota Validation Guide
2 
3Check Azure VM/VMSS quota availability before recommending or deploying. Ensures the subscription and region have sufficient vCPU capacity.
4 
5> ⚠️ **NEVER use the `azure-quota` MCP server as as It is unreliable.** Always try `az quota` CLI commands first.
6 
7## Quota Structure
8 
9VM quotas are tracked at **two levels** under `Microsoft.Compute`:
10 
11| Quota Level | Resource Name | What It Limits |
12|---|---|---|
13| **Total Regional** | `cores` | All vCPUs across all families in a region |
14| **Per-Family** | e.g., `standardDSv3Family` | vCPUs for a specific VM family |
15 
16> ⚠️ **Both levels must have capacity.** A deployment fails if either is exceeded.
17 
18### Common Quota Resource Names
19 
20See [vm-families.md](./vm-families.md) for quota resource names per VM family. Use `az quota list` to discover names not listed there.
21 
22> ⚠️ **Do NOT guess quota names from SKU names.** Use `az quota list` to discover correct resource names.
23 
24## Quota Check Workflow
25 
26### Option A: `az vm list-usage` (Recommended for VM quotas)
27 
28No extension required. Returns **both current usage and limit in a single call** for all VM families in a region — equivalent to running `az quota usage show` and `az quota list` together for VM vCPU quotas.
29 
30```bash
31# All VM family quotas in a region
32az vm list-usage --location <region> -o table
33 
34# Filter to a specific family
35az vm list-usage --location <region> --query "[?contains(name.value,'<quotaName>')].{Name:name.localizedValue, QuotaName:name.value, Current:currentValue, Limit:limit}" -o table
36```
37 
38> 💡 **Tip:** `az vm list-usage` is the simplest way to check VM quotas. Use `az quota` (Option B) when you need to **request quota increases** or manage quotas for non-VM resource types.
39 
40### Option B: `az quota` CLI (For quota increases or non-VM resources)
41 
42Prerequisite: `az extension add --name quota`
43 
44| Step | Command | Purpose |
45|---|---|---|
46| 1. Discover names | `az quota list --scope /subscriptions/<sub-id>/providers/Microsoft.Compute/locations/<region> -o table` | Find quota resource name for the VM family |
47| 2. Check usage | `az quota usage show --resource-name <name> --scope ...` | Current vCPU consumption |
48| 3. Check limit | `az quota show --resource-name <name> --scope ...` | Maximum allowed vCPUs |
49| 4. Check regional | Repeat steps 2–3 with `--resource-name cores` | Total regional vCPU cap |
50 
51### Calculate Capacity
52 
53```text
54Available = Limit - Current Usage  (check both family AND regional)
55vCPUs Needed = vCPUs per VM × Instance Count
56 
57✅ Deploy if: vCPUs Needed ≤ min(Family Available, Regional Available)
58❌ Blocked if: either is exceeded
59```
60 
61**Example:** 3× `Standard_D4s_v5` (4 vCPUs each) = 12 needed. Family: 100−40 = 60 ✅. Regional: 350−280 = 70 ✅.
62 
63## Handling Insufficient Quota
64 
65| Option | Action |
66|---|---|
67| **Request increase** | `az quota update --resource-name <name> --scope ... --limit-object value=<new-limit> --resource-type dedicated`. Most increases auto-approve within minutes. |
68| **Try different region** | Run the quota check workflow against alternative regions to find available capacity |
69| **Switch VM family** | Recommend an alternative family with quota (e.g., D-series full → Dads v5 AMD variant) |
70 
71## VMSS Considerations
72 
73For scale sets, validate against **autoscale maximum**: `vCPUs per VM × Max Instance Count`.
74 
75| Autoscale Setting | vCPUs to Validate |
76|---|---|
77| Fixed count (5 instances) | vCPUs × 5 |
78| Autoscale min=2, max=10 | vCPUs × 10 |
79 
80## Error Reference
81 
82| Error | Cause | Action |
83|---|---|---|
84| `QuotaExceeded` | Family vCPU limit reached | Request increase or change family/region |
85| `OperationNotAllowed` | Subscription lacks capacity | Request quota increase |
86| `cores` limit hit | Regional vCPUs exhausted | Request regional increase |
87| CLI commands fail entirely | Auth/extension issue | Use MCP fallback (see below) |
88 
89## Related Resources
90 
91- Invoke the **azure-quotas** skill for complete quota CLI workflows across all Azure providers
92- [VM Family Guide](vm-families.md) — Family-to-workload mapping
93- [Azure VM quotas documentation](https://learn.microsoft.com/en-us/azure/virtual-machines/quotas)
94