Performance Tuning

Performance Tuning

Default settings work for most setups. The options below are useful when you have a large library, limited hardware, or want to control how aggressively Mimick uses bandwidth and memory.

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Upload Workers

Setting: Settings → Behavior → Upload Workers (1–10, default 3)

Each worker is an independent async upload task. Workers share the same HTTP connection pool, so adding more workers increases concurrent uploads rather than opening separate connections.

Scenario	Suggested value
Slow or metered connection	1–2
Home LAN, typical library	3 (default)
Fast LAN or local server, large backlog	5–8
Saturating uploads cause other issues	Reduce back toward default

Workers apply to the background sync engine only. Album sync (triggered from the library view) runs as a separate task and is not affected by this setting.

Changing the worker count takes effect immediately after saving — no restart needed.

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Startup Catch-Up Mode

Setting: Settings → Behavior → Startup Catch-Up Mode

Controls how much work Mimick does each time it launches.

Mode	What it does	When to use it
Full	Hashes every file in every watch folder	Initial setup; after adding many new folders
Recent Only	Hashes files modified in approximately the last 7 days	Ongoing use with occasional gaps
New Files Only	Only processes files not already in the sync index	Daily driver once the library is fully synced

Switch from Full to New Files Only once your initial sync is complete. Startup time on a large library (tens of thousands of files) drops significantly.

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Thumbnail Memory Cache

Setting: Settings → Behavior → Thumbnail Memory Cache (MB, default 80, range 16–1024)

The library view decodes thumbnails into RAM for fast rendering. This cap controls how much memory decoded thumbnails can occupy before older entries are evicted.

• Increasing the cap speeds up scrolling back through previously visited pages.
• Decreasing it frees RAM at the cost of re-fetching thumbnails when scrolling back.
• On systems with limited RAM, leave at default or reduce to 32–48 MB.
• On systems with ≥16 GB RAM and a large library, 256–512 MB can noticeably reduce re-fetches.

Changing the cache size takes effect after restarting Mimick.

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Full-Resolution Preview

Setting: Settings → Behavior → Full-Resolution Preview (switch, default off)

When off, the lightbox loads a ~1440px server-generated preview image. When on, it loads the original file.

• Full-resolution mode uses significantly more bandwidth and takes longer to load on slow connections.
• Use it only if you need to inspect originals or are on a fast LAN connection to your Immich server.

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Large Libraries: Recommended Configuration

For libraries with more than ~50,000 files:

1. Set Startup Catch-Up Mode to New Files Only after the initial sync.
2. Keep Upload Workers at 3–5 unless uploads are a bottleneck.
3. Set Thumbnail Memory Cache to 256 MB or higher if RAM allows.
4. Leave Full-Resolution Preview off unless needed.