Tối ưu tốc độ

Xác định nút cổ chai

Sync chậm có 4 nguyên nhân chính, từ frequent → rare:

1. Disk read source (Syncthing đọc file để hash)
2. Hash CPU (SHA-256 từng block)
3. Network bandwidth
4. File watcher overhead

Quick diagnostic

# Web UI → folder card → check progress
# Nếu Local State đang scan → bottleneck #1 hoặc #2
# Nếu Syncing % chậm progress → bottleneck #3
# Nếu "Out of Sync" mãi không clear → bottleneck #4

Nút cổ chai cross-OS (Windows ↔ WSL)

⚠ Most common issue.

Windows Syncthing process
        ↓
  Đọc file qua \\wsl.localhost\ (9P bridge)   ← BOTTLENECK
        ↓
  WSL ext4 filesystem

Symptom: scan rate ~20-50 MB/min cho WSL folders.

Fix: Cài Syncthing native trong WSL — xem Setup WSL. Speedup ~120x.

Quá nhiều file nhỏ

Folders với nhiều files nhỏ (vd .git/objects/, node_modules/) — overhead per-file > content transfer.

Numbers thực tế:

• 70,000 files × ~1ms open/hash/close = 70 giây pure overhead
• Network may be idle most of time waiting for file ops

Fix:

Strict ignore patterns

# Build artifacts (huge file count)
**/node_modules
**/.next
**/dist
**/build

# Git internals (many small objects)
**/.git/objects/pack
**/.git/lfs

# Caches
**/.cache
**/__pycache__

Folder consolidation

Sync 1 large folder thay vì 10 small folders nếu cùng pattern. Reduce metadata overhead.

CPU hash là nút cổ chai

Syncthing hash SHA-256 mỗi block 128KB. Trên CPU yếu (vd Atom, ARM low-end), hash speed ~50-100 MB/s.

Check Syncthing log:

[CEXGR] INFO: Single thread SHA256 performance is 368 MB/s
[CEXGR] INFO: Hashing performance is 307.73 MB/s

→ Đó là max throughput hash trên máy này.

Fix:

• Hardware: SSD + modern CPU = 300+ MB/s
• Settings: increase Max File Pull Concurrency (Settings → Advanced → Folder Settings)

Băng thông mạng

LAN gigabit theoretical 125 MB/s, practical 80-100 MB/s sau TCP overhead.

Check actual rate:

# Web UI → Remote Devices → device card → Download Rate / Upload Rate

Nếu rate << bandwidth (vd LAN gigabit nhưng chỉ 5 MB/s):

• Bottleneck KHÔNG phải network
• Likely là disk read source hoặc small file overhead

File watcher không tin cậy

Symptom: edit file → Syncthing không detect → phải Force Rescan manually.

Causes:

• Cross-OS access (\wsl.localhost) — file events lost
• Network mounts (CIFS, NFS) — watch fail
• WSL2 native ext4 — work OK
• Windows NTFS native — work OK

Fix:

• Set Rescan Interval ngắn hơn (Web UI → folder edit → Advanced → Rescan Interval): default 3600s (1h), set 60-300s
• Hoặc disable Watch for Changes + rely on rescan

Indexing database

Syncthing maintain database ~/.config/syncthing/index-v0.14.0.db/ (Linux) hoặc %APPDATA%\Syncthing\ (Windows). Database growth có thể slow over time.

Fix nếu Syncthing càng chạy càng chậm:

# Stop Syncthing
pkill -f syncthing

# Backup config
cp -r ~/.config/syncthing ~/.config/syncthing.bak

# Reset index database (sẽ re-scan all folders)
rm -rf ~/.config/syncthing/index-v0.14.0.db

# Restart
syncthing serve --no-browser &

⚠ Re-scan all folders sẽ tốn time tương tự initial scan. Chỉ làm khi cần.

Cài đặt nén

Default Syncthing compression: Metadata Only. Cho text-heavy folders, switch sang All Data có thể giảm bandwidth 30-50%:

Web UI → Edit Device → Advanced → Compression: All Data

⚠ Trade-off CPU usage tăng cho compression. Acceptable cho small files, bad cho large media.

Tinh chỉnh nâng cao

Settings → Advanced → Folder Settings:

  Max Folder Concurrency: 4 (default 0 = unlimited)
  Pull Order: Random (default) hoặc Newest First (cho time-sensitive)
  Disable Sparse Files: false (default)

Settings → Advanced → Connections:

  Max Send/Receive Rate: 0 (unlimited) hoặc throttle nếu chia sẻ network

Benchmark tốc độ thực tế

Em đã measure trên setup AIWS production (mid-range workstation + LAN gigabit):

Folder	Path type	Files	Size	Initial scan	Sync rate
~/.claude/	Native NTFS	1,989	104 MB	30s	~50 MB/s
D:/Public LAN Folder/	Native NTFS	31,484	8.3 GB	3 min	~80 MB/s
~/projects/ (Win 9P)	Cross-OS 9P	70,640	1 GB scanned	❌ never finished	46 KiB/s
/home/x/projects/ (WSL native)	Native ext4	107,588	6.11 GB	95s	~5 MB/s small files

Insights:

• Native paths >> cross-OS
• Small file overhead dominate trên 6.11 GB / 107k files (avg ~60KB/file → too many syscalls)
• LAN bandwidth không phải bottleneck cho code projects (chủ yếu small files)

Bước tiếp theo

• Common issues — không phải performance issue
• Architecture — design choices ảnh hưởng performance