BarnacleBoy
3c11190822
- docs/sbc-selection.md: full rewrite for OPi 3B specs (RK3566, 8GB, 256GB eMMC, built-in WiFi) - README.md: SBC description, checklist, components table, quick ref, cost estimate - docs/parts-list.md: SBC marked purchased, eMMC/controller/WiFi changes - docs/design-decisions.md: WiFi exclusion reason, native eDP, power input - docs/salvage-analysis.md: WiFi card not needed, cooling fan, summary tables - docs/storage-architecture.md: rewritten for 256GB eMMC primary boot - docs/usb-expansion.md: 2x USB3 native, port allocation, power budget - docs/port-layout.md: OPi3B port differences (eDP, power-only USB-C, built-in WiFi) - docs/power-system.md: lower power draw context
176 lines
No EOL
5.2 KiB
Markdown
176 lines
No EOL
5.2 KiB
Markdown
# Storage Architecture
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**Strategy:** 256GB onboard eMMC for boot/root/data. SD card and M.2 for expansion.
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---
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## Design Principles
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1. **Simplicity:** eMMC boots out of the box, faster and more reliable than SD
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2. **Speed:** eMMC ~300 MB/s read — comparable to a SATA SSD
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3. **Capacity:** 256GB onboard is plenty for OS + apps + projects + media
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4. **Flexibility:** MicroSD and M.2 slots available for expansion
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5. **Cost:** Included with SBC — no separate purchase needed
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---
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## Layer 1: Boot/Root (eMMC)
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The Orange Pi 3B boots from its onboard 256GB eMMC by default. This is the primary storage:
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### eMMC Performance
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| Attribute | Value |
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|-----------|-------|
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| Capacity | 256GB |
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| Interface | eMMC 5.1 |
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| Sequential read | ~300 MB/s |
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| Sequential write | ~200 MB/s |
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| Reliability | Significantly better than SD cards |
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### Partition Layout (Suggested)
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```
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/dev/mmcblk1 (eMMC, 256GB)
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├── /dev/mmcblk1p1 → /boot (fat32, ~500MB)
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├── /dev/mmcblk1p2 → / (ext4, ~80GB)
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├── /dev/mmcblk1p3 → /home (ext4, ~170GB)
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└── (remaining for swap or data)
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```
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Or simpler:
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```
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/dev/mmcblk1p1 → /boot (fat32, ~500MB)
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/dev/mmcblk1p2 → / (ext4, all remaining)
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/home → subdirectory, not separate partition
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```
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256GB is large enough that separate partitions are optional. A single root partition with everything under it works fine.
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### Boot Configuration
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Default OPi3B boots from eMMC when populated. No configuration needed.
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---
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## Layer 2: Expansion (MicroSD + M.2)
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### MicroSD
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| Attribute | Value |
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|-----------|-------|
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| Slot | Standard push-push |
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| Max capacity | Up to 512GB |
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| Use | Backup, media library, test OS images |
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No need for endurance-rated card — the SD slot is now secondary storage, not primary boot.
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### M.2 M-key
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| Interface | Speed | Notes |
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|-----------|-------|-------|
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| PCIe 2.0 x1 | ~300 MB/s | Slightly slower than eMMC |
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| SATA III | ~550 MB/s | Faster than eMMC (if SATA SSD) |
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Can add NVMe or SATA SSD for bulk storage if 256GB eMMC fills up. M.2 slot shares bandwidth with USB 3.0 — both use the same PCIe controller.
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---
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## Layer 3: Data Storage (USB)
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Optional external storage for:
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- Large media libraries
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- Project archives
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- System backups
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### Options
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| Option | Speed | Cost | Notes |
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|--------|-------|------|-------|
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| USB 3.0 SATA enclosure | ~400 MB/s | $10-15 | Reuse 2.5" drives |
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| USB 3.0 NVMe enclosure | ~400 MB/s | $8-15 | Compact |
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| USB flash drive (fast) | 200-400 MB/s | $15-25 | Kingston, Samsung BAR |
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### Mount Strategy
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```bash
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# /etc/fstab (optional USB storage)
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UUID=<ssd-uuid> /mnt/data ext4 defaults,noatime 0 2
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/mnt/data/projects /home/jez/projects none bind 0 0
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/mnt/data/media /home/jez/media none bind 0 0
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```
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---
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## Storage Layout
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```
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┌─────────────────────────────────────┐
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│ eMMC (/dev/mmcblk1) │
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│ 256GB onboard │
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│ ├── /boot (fat32, 500MB) │
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│ ├── / (ext4, ~80GB) │
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│ └── /home (ext4, ~175GB) │
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│ OS + apps + projects + media │
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└─────────────────────────────────────┘
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┌─────────────────────────────────────┐
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│ MicroSD (/dev/mmcblk0) │
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│ Optional expansion │
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│ ├── OS images / boot tests │
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│ └── Media library / backups │
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└─────────────────────────────────────┘
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┌─────────────────────────────────────┐
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│ USB SSD (/dev/sda) │
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│ Optional — only if eMMC fills up │
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│ ├── /mnt/data/projects │
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│ ├── /mnt/data/media │
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│ └── /mnt/data/backup │
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└─────────────────────────────────────┘
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```
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---
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## Backup Strategy
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### eMMC Imaging
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```bash
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# Backup entire eMMC to USB drive
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sudo dd if=/dev/mmcblk1 of=/mnt/data/cyberdeck-emmc-backup.img bs=4M status=progress
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# Restore
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sudo dd if=/mnt/data/cyberdeck-emmc-backup.img of=/dev/mmcblk1 bs=4M status=progress
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```
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### Data Backup
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- Timeshift for system snapshots
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- rsync to external drive
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- Cloud sync for critical files
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---
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## Performance Expectations
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| Operation | eMMC | MicroSD | USB SSD |
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|-----------|------|---------|---------|
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| Boot time | ~5-8s | ~10-15s | ~5-8s |
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| App launch | 0.5-1s | 1-3s | 0.5-1s |
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| File read (1GB) | ~3-4s | ~40-90s | ~3-5s |
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| Reliability | Excellent | Poor (wear) | Good |
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eMMC is the clear winner for boot and everyday use. SD card and USB storage are optional extras.
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---
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## Cost Summary
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| Item | Low | High | Status |
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|------|-----|------|--------|
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| 256GB eMMC | $0 | $0 | **Included with SBC** |
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| MicroSD (optional) | $0 | $15 | Only if needed |
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| USB enclosure (optional) | $0 | $15 | Only if eMMC fills up |
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| **Total** | **$0** | **$30** | | |