BarnacleBoy 3c11190822 update all docs: Orange Pi 3B 8GB purchased (89)

- 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

2026-05-24 06:51:26 +00:00

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Storage Architecture

Strategy: 256GB onboard eMMC for boot/root/data. SD card and M.2 for expansion.

Design Principles

Simplicity: eMMC boots out of the box, faster and more reliable than SD
Speed: eMMC ~300 MB/s read — comparable to a SATA SSD
Capacity: 256GB onboard is plenty for OS + apps + projects + media
Flexibility: MicroSD and M.2 slots available for expansion
Cost: Included with SBC — no separate purchase needed

Layer 1: Boot/Root (eMMC)

The Orange Pi 3B boots from its onboard 256GB eMMC by default. This is the primary storage:

eMMC Performance

Attribute	Value
Capacity	256GB
Interface	eMMC 5.1
Sequential read	~300 MB/s
Sequential write	~200 MB/s
Reliability	Significantly better than SD cards

Partition Layout (Suggested)

/dev/mmcblk1 (eMMC, 256GB)
├── /dev/mmcblk1p1  → /boot (fat32, ~500MB)
├── /dev/mmcblk1p2  → / (ext4, ~80GB)
├── /dev/mmcblk1p3  → /home (ext4, ~170GB)
└── (remaining for swap or data)

Or simpler:

/dev/mmcblk1p1  → /boot (fat32, ~500MB)
/dev/mmcblk1p2  → / (ext4, all remaining)
    /home       → subdirectory, not separate partition

256GB is large enough that separate partitions are optional. A single root partition with everything under it works fine.

Boot Configuration

Default OPi3B boots from eMMC when populated. No configuration needed.

Layer 2: Expansion (MicroSD + M.2)

MicroSD

Attribute	Value
Slot	Standard push-push
Max capacity	Up to 512GB
Use	Backup, media library, test OS images

No need for endurance-rated card — the SD slot is now secondary storage, not primary boot.

M.2 M-key

Interface	Speed	Notes
PCIe 2.0 x1	~300 MB/s	Slightly slower than eMMC
SATA III	~550 MB/s	Faster than eMMC (if SATA SSD)

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.

Layer 3: Data Storage (USB)

Optional external storage for:

Large media libraries
Project archives
System backups

Options

Option	Speed	Cost	Notes
USB 3.0 SATA enclosure	~400 MB/s	$10-15	Reuse 2.5" drives
USB 3.0 NVMe enclosure	~400 MB/s	$8-15	Compact
USB flash drive (fast)	200-400 MB/s	$15-25	Kingston, Samsung BAR

Mount Strategy

# /etc/fstab (optional USB storage)
UUID=<ssd-uuid> /mnt/data    ext4    defaults,noatime    0  2
/mnt/data/projects /home/jez/projects  none    bind    0  0
/mnt/data/media   /home/jez/media     none    bind    0  0

Storage Layout

┌─────────────────────────────────────┐
│  eMMC (/dev/mmcblk1)               │
│  256GB onboard                      │
│  ├── /boot     (fat32, 500MB)      │
│  ├── /         (ext4, ~80GB)       │
│  └── /home     (ext4, ~175GB)      │
│      OS + apps + projects + media  │
└─────────────────────────────────────┘

┌─────────────────────────────────────┐
│  MicroSD (/dev/mmcblk0)            │
│  Optional expansion                 │
│  ├── OS images / boot tests         │
│  └── Media library / backups        │
└─────────────────────────────────────┘

┌─────────────────────────────────────┐
│  USB SSD (/dev/sda)                │
│  Optional — only if eMMC fills up   │
│  ├── /mnt/data/projects             │
│  ├── /mnt/data/media                │
│  └── /mnt/data/backup               │
└─────────────────────────────────────┘

Backup Strategy

eMMC Imaging

# Backup entire eMMC to USB drive
sudo dd if=/dev/mmcblk1 of=/mnt/data/cyberdeck-emmc-backup.img bs=4M status=progress

# Restore
sudo dd if=/mnt/data/cyberdeck-emmc-backup.img of=/dev/mmcblk1 bs=4M status=progress

Data Backup

Timeshift for system snapshots
rsync to external drive
Cloud sync for critical files

Performance Expectations

Operation	eMMC	MicroSD	USB SSD
Boot time	~5-8s	~10-15s	~5-8s
App launch	0.5-1s	1-3s	0.5-1s
File read (1GB)	~3-4s	~40-90s	~3-5s
Reliability	Excellent	Poor (wear)	Good

eMMC is the clear winner for boot and everyday use. SD card and USB storage are optional extras.

Cost Summary

Item	Low	High	Status
256GB eMMC	$0	$0	Included with SBC
MicroSD (optional)	$0	$15	Only if needed
USB enclosure (optional)	$0	$15	Only if eMMC fills up
Total	$0	$30

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