Use Case: Multi-USB Dataset Transfer

Scenario

Transfer a large dataset (e.g., machine learning models, video collection) that requires multiple USB drive swaps due to size constraints.

Use Case: Multi-USB Dataset Transfer UC-TRANSFER-003

status: approved tags: transfer, workflow, multi-usb, swap release: v1.0 specifies: FR-TRANSFER-002, FR-TRANSFER-006, FR-TRANSFER-008, FR-TRANSFER-012, FR-TRANSFER-013, FR-TRANSFER-024, FR-TRANSFER-025, FR-TRANSFER-026

Transfer large dataset (30GB) requiring multiple USB swaps with small capacity drives (4x 8GB USBs). Pack: Split dataset into chunks matching USB capacity, prompt for USB swaps during packing, write manifest to each USB for independent verification. Transfer: Transport all USB drives across air-gap (together or separately). Unpack: Support progressive unpack with USB swaps, process USBs in any order, verify each chunk before extraction, resume if interrupted mid-swap. Acceptance Criteria: Handle 4+ USB swaps without errors, clear prompts for USB insertion, verify integrity across all chunks, work with USBs in any order.

---

Prerequisites

• Source machine: Connected system with data to transfer

• Destination machine: air-gapped system

• Transfer media: Four 8GB USB drives (only have small USBs available)

• Dataset: ~/ml-models/ (30GB total)

---

Workflow Steps

Phase 1: Pack with Multiple USB Swaps

Initial pack command

airgap-transfer pack ~/ml-models/ /media/usb-drive --chunk-size 8GB

USB swap sequence

• USB #1: Writes chunk_000.tar (8GB)

  • Tool: “Chunk 1 of 4 complete. Insert next USB.”

  • User: Eject USB #1, insert USB #2

• USB #2: Writes chunk_001.tar (8GB)

  • Tool: “Chunk 2 of 4 complete. Insert next USB.”

  • User: Eject USB #2, insert USB #3

• USB #3: Writes chunk_002.tar (8GB)

  • Tool: “Chunk 3 of 4 complete. Insert next USB.”

  • User: Eject USB #3, insert USB #4

• USB #4: Writes chunk_003.tar (6GB, final chunk)

  • Tool: “Pack complete. 4 chunks created.”

Manifest on each USB

• Each USB contains a copy of airgap-transfer-manifest.json

• Manifest lists all 4 chunks with checksums

• User can verify any USB independently

Phase 2: Physical Transfer

• Transport all 4 USB drives across air-gap

• USBs can be transported together or separately

Phase 3: Unpack on Destination

Check available chunks

• Connect USB #1

airgap-transfer list /media/usb-1

Shows: chunk_000 available (1 of 4)

Progressive unpack

• Option A: Connect all USBs, unpack once

# Mount all USBs
airgap-transfer unpack /media/usb-drives ~/restored-models/

• Option B: Connect USBs one at a time

# Connect USB #1
airgap-transfer unpack /media/usb-1 ~/restored-models/
# Tool: "Waiting for chunk_001. Insert USB with chunk_001."
# User swaps to USB #2, tool continues

Verification

• Tool verifies each chunk before extraction

• Final verification after all chunks extracted

• Reports: “30GB transferred across 4 USBs, verified”

---

Acceptance Criteria

• ✅ Handle 4+ USB swaps without errors

• ✅ Resume if interrupted mid-swap

• ✅ Clear prompts for USB insertion

• ✅ Verify integrity across all chunks

• ✅ Work with USBs in any order

---

Edge Cases

Scenario	Behavior
USBs inserted out of order	Tool processes in chunk index order
Missing USB during unpack	Tool prompts for specific chunk number
Duplicate chunk on multiple USBs	Tool uses first found, warns of duplicate
Interrupted during USB swap	Resume from last completed chunk

---

User Experience Notes

Prompts should be clear and specific:

• ❌ Bad: “Insert next USB”

• ✅ Good: “Chunk 2 of 4 complete. Insert USB for chunk 3.”

Progress indication:

• Show overall progress: “18GB of 30GB transferred (60%)”

• Show chunk progress: “Chunk 3/4: 8GB written”

Linked Requirements

ID	Title	Status	Release	Verified By
FR-TRANSFER-002	Auto-Detect USB Capacity	approved	v1.0	TC-PCK-003
FR-TRANSFER-006	Manual Chunk Size Specification	approved	v1.0	TC-PCK-007
FR-TRANSFER-008	Prompt for USB Swapping	approved	v1.0	TC-PCK-009
FR-TRANSFER-012	Validate Chunk Completeness	approved	v1.0	TC-UNP-004
FR-TRANSFER-013	Resume Partial Unpacks	approved	v1.0	TC-UNP-005
FR-TRANSFER-024	Maintain Operation State	approved	v1.0	TC-STA-001
FR-TRANSFER-025	Track Chunk Completion	approved	v1.0	TC-STA-002
FR-TRANSFER-026	Resume Interrupted Pack	approved	v1.0	TC-STA-003

Traceability

Tests

Integration Tests

No needs passed the filters

Unit Tests of Linked Requirements

ID	Title	Status	Tests
TC-PCK-003	Auto-Detect USB Capacity	approved
TC-PCK-007	Manual Chunk Size Specification	approved
TC-PCK-009	USB Swapping Prompt	approved
TC-STA-001	Persist Operation State	approved
TC-STA-002	Track Chunk Completion	approved
TC-STA-003	Resume Interrupted Pack	approved
TC-UNP-004	Validate Chunk Completeness	approved
TC-UNP-005	Resume Partial Unpack	approved