Distributing Large Map Updates: Compression & Repack Tips for Arc Raiders Creators

Stop wasting bandwidth on giant map updates — practical compression and repack tactics for Arc Raiders creators

Hook: If you maintain Arc Raiders map mods or community maps and you dread the upload/upload-and-seed cycle every time Embark rolls out a new map or you tweak assets, this guide is for you. Large .pak files, chunky textures and multi-gig updates kill seed ratios, fragment downloads, and invite corruption complaints. In 2026 the expectations are higher: players want smaller updates, fast partial downloads, provable integrity, and working magnet links. This guide shows you how to compress, chunk, patch and seed large Arc Raiders map updates for efficient torrent distribution while preserving in-game performance and data integrity.

Top-line recommendations (the inverted pyramid)

• Split by logical units: Distribute maps or major asset groups as separate files/torrents so clients can download only what they need.
• Use modern compression: Zstandard (zstd) with dictionaries for repeatable assets; use --long for long-range matches on huge binary .pak/.arc files.
• Provide deltas: Offer xdelta3 (or bsdiff for executables) patches between versions to keep updates small.
• Optimize torrent metadata: Choose piece size appropriate to total size (1–4 MiB typical for 10–200 GiB ranges) and create hybrid v1/v2 torrents when possible.
• Guarantee integrity: Publish SHA256 sums and PGP-signed manifest; include PAR2 for recovery if you expect peer churn.
• Seed smart: Use seedboxes, webseeds, and initial seeding modes; publish magnet links and trackers; keep older versions seeded for patching efficiency.

Why this matters in 2026

Embark's 2026 roadmap for Arc Raiders includes multiple new maps of varying sizes — some smaller and some "grander than what we've got now" — and community creators will be reworking old maps and swapping assets to match official updates. Torrent clients and infrastructure have evolved: BitTorrent v2 adoption accelerated in late 2025, seedboxes now routinely support NVMe + 10–40 Gbps, and compression tools like zstd (1.5+) and selective-dictionary workflows became mainstream. Players expect fast, safe updates that don't waste bandwidth or disk space.

What changed recently

• BitTorrent v2 increased integrity guarantees with SHA-256 and Merkle trees — use hybrid torrents for better compatibility.
• zstd dictionaries and long-range matching let you compress repeated textures/meshes far better than generic compressors.
• Seedbox providers and cheap CDN-backed webseeds make small-seed-era distribution feasible; combine these with torrenting for resilience.

Step-by-step workflow: From raw map to efficient torrent

1) Analyze the map package

1. List files and sizes (ls -lh or tree -sh). Identify very large files (.pak/.pakchunk, .uasset, .umap, texture atlases and audio banks).
2. Classify by change frequency: static assets (terrain meshes), iterative assets (textures, level edits), and code/executables. Prioritize keeping static assets unchanged to maximize delta efficiency.
3. Detect compressibility: run file-type checks (file command) and test compressibility on samples. Already compressed items (PNG, JPG, OGG) rarely compress further; textures in raw DDS or uncompressed formats compress well.

2) Choose a distribution layout

Design the file layout for torrent friendliness:

• Per-map torrents: Each map shipped as its own torrent + optional asset pack. Easier for players to grab only maps they need and for seeds to specialize.
• Asset packs: Share large shared packs as a separate torrent (e.g., textures_common_v3.pak). This avoids reuploading the same textures across multiple map torrents.
• Meta-torrent or bundle: Offer a single bundle for players who want everything; make it optional but maintain per-map archives for partial downloads.

3) Repack with modern compressors

Use zstd for best balance of speed and compression on 2026 hardware. A typical workflow:

1. Create a dictionary when you have many similar files across versions: zstd --train --output=dict.zst sample/*.bin
2. Compress with the dictionary and long-range matching for large binary blobs (pak files): zstd --ultra -22 --long=31 --no-check -T0 --dict=dict.zst input.pak -o input.pak.zst

Notes:

• Dictionary gains: If you maintain iterative maps, zstd dictionaries cut repetitious texture/mesh copies across maps dramatically.
• Don't recompress already compressed assets: Containerize but avoid compressing PNG/JPEG/OGG again — store them as-is in the archive to enable partial extraction and faster patching.
• Store file lists: Keep a manifest listing internal file paths and CRCs — this helps delta tools and integrity checks later.

4) Create delta patches — the most bandwidth-efficient option

Players hate downloading full 20–50 GB map files when only small portions changed. Offer delta patches between released versions so users can patch their existing files instead of re-downloading full assets.

• For large binary blobs (.pak): use xdelta3 to create source-based deltas. Example: xdelta3 -e -s old.pak new.pak patch.xdelta
• For executables or small binary changes: bsdiff sometimes yields smaller patches but is slower for huge files. Example: bsdiff old.exe new.exe patch.bsdiff
• If you distribute via HTTP as well as torrents, provide zsync/rdiff signatures so clients can patch using their local content without requiring a full re-download.

Practical tip: Always verify that a patch applies cleanly on a fresh copy of old.pak and include an automated integrity check in your patch installer.

5) Prepare torrent metadata with seeding and piece-size in mind

Torrent piece size impacts download efficiency and metadata size. General guidelines:

• For totals 1–10 GiB: 256 KiB–512 KiB pieces
• For 10–50 GiB: 1 MiB pieces
• For 50–200 GiB: 2–4 MiB pieces
• For >200 GiB: 4–8 MiB pieces

Why this matters: too-small pieces generate huge .torrent metadata and more checksums; too-large pieces make rare-piece availability worse on low-seed swarms.

Other torrent metadata considerations:

• Create hybrid v1+v2 torrents if your creation tool supports it (v2 brings SHA-256 and per-file integrity while v1 keeps compatibility).
• Include webseeds: If you have an HTTP mirror or seedbox, add it as a webseed so clients can fall back to HTTP when swarm seeds are low.
• Pick trackers carefully: Use a mix of public trackers, reliable community trackers and your own tracker if available. DHT and Peer Exchange (PEX) should be left enabled.
• Publish a magnet link: Always publish magnet links with the exact infohash and display the torrent size and piece size in your release notes.

6) Seed smart: initial and ongoing strategies

Seed quality matters more than raw seed count. Recommended seeding approach:

1. Initial seeding / super-seeding: If you're the only initial source, enable super-seed on your uploader to help the swarm replicate unique pieces faster.
2. Use a seedbox for first 48–72 hours: A 10+ Gbps NVMe seedbox stabilizes the swarm quickly and preserves your home upload cap.
3. Keep multiple seeds and mirrors: Maintain at least two unrelated seeds (e.g., seedbox + home server) for resilience.
4. Webseeds and CDN mirroring: When possible, store one canonical copy on a cheap CDN-backed HTTP mirror and list it as a webseed to reduce strain on P2P when the torrent is new.

7) Integrity and user trust

Players need to trust the files they download. Make verification simple and automated:

• Provide SHA256SUMS for every delivered file and sign that manifest with your PGP key: sha256sum * > SHA256SUMS; gpg --detach-sign --armor SHA256SUMS
• Include in-client verifications: Encourage users to use torrent clients that validate piece hashes (most do) and use BitTorrent v2 for stronger guarantees.
• PAR2 for recovery: Create PAR2 files for big releases so users with partial downloads or corrupt pieces can reconstruct missing data without re-downloading everything: par2 create -r10 map_pack.par2 map_pack/*
• Publish install and verification steps: Show checksum verification, how to apply delta patches, and a minimal troubleshooting section to reduce support requests.

8) Test end-to-end (mandatory)

Before posting a public release, do this checklist:

1. Seed a private test torrent and verify magnet resolves to your client.
2. Apply delta patches on a clean install and verify the map loads and runs in-game (test on low-end and high-end machines).
3. Test interrupted downloads and verify PAR2 recovery.
4. Verify SHA256 manifests and PGP signatures validate on other machines.

Advanced strategies and optimizations

Dictionary-based repacks across map generations

When you maintain many incremental versions of the same map family, create a shared zstd dictionary from previous versions to drastically reduce both full repack sizes and delta sizes. Workflow:

1. Collect representative files from past releases (textures, common meshes).
2. zstd --train --output=mydict.dict samples/*
3. Compress new packs with --dict=mydict.dict and --long for the best cross-version compression.

Case note: In community testing during late 2025, using dictionaries often reduced repetitive texture packs by 20–40% versus no-dict zstd.

Content-defined chunking for better deltas

Traditional block-based deltas (xdelta) can break when files shift. Consider content-defined chunking (CDC) with librsync/rdiff for asset trees — it is more resilient to insertions and produces smaller reconstructions in many cases. Use rdiff or zsync-compatible tools if you plan HTTP fallback patching.

When to skip deltas and offer full repacks

Sometimes deltas are worse than full downloads (e.g., if internal file ordering changes or compression schemes change). In those cases:

• Offer both: a small delta and the full repack labeled clearly so users choose.
• Explain when to use each (delta for within-version small updates, full repack for layout or engine upgrades).

Practical commands cheat-sheet

• Make zstd dictionary: zstd --train --output=dict.zst samples/*
• Compress with dict + long-range: zstd --ultra -22 --long=31 --dict=dict.zst -T0 input.pak -o input.pak.zst
• Create xdelta patch: xdelta3 -e -s old.pak new.pak patch.xdelta
• Apply xdelta patch: xdelta3 -d -s old.pak patch.xdelta new.pak
• Create PAR2 files: par2 create -r10 release.par2 folder/*
• Generate SHA256 sums: sha256sum * > SHA256SUMS
  Sign sums: gpg --detach-sign --armor SHA256SUMS

Case study: compressing an Arc Raiders-style map update (example)

Scenario: You have a 32 GiB map package (large .pak with textures and meshes). You made art tweaks and a few new geometry assets for a 2026 map refresh.

1. Analyze: 22 GiB of textures, 5 GiB meshes, 3 GiB audio/other.
2. Create dictionary from prior version textures and compress textures separately with zstd --dict and --long. Textures compress 30–40% better with a trained dict.
3. Repack meshes and audio without aggressive recompression (audio and already-compressed textures stored as-is inside container to allow quick patching).
4. Create xdelta between old.pak and new.pak. Patch size ends up ~450–900 MiB depending on reordering — acceptable compared to 32 GiB full re-download.
5. Publish: per-map torrent (compressed), patch torrent (xdelta + installer), and a webseed for the full repack. Include SHA256 and PAR2 for recovery.

Result: Most users apply the small patch; those who need the full package have it available. Bandwidth saved across the first week of release is often >90% compared to forcing a full re-download.

Troubleshooting & common pitfalls

• Poor patch sizes: Likely caused by reordering or compressing and recompressing content. Keep stable internal file order and avoid altering in-place compressed assets.
• Clients failing to verify: Check for correct piece size in torrent metadata and ensure you created hybrid v1+v2 if you want compatibility across clients.
• Low seed availability: Add webseeds, encourage community mirrors, and consider seeding on a couple of public trackers in addition to private ones.
• Performance regressions in-game: Test repacked loads; if packed archives change I/O patterns in-game, prefer shipping assets unpacked or in the original engine container format.

Pro tip: In 2026, combine a small xdelta patch with an optional full zstd-compressed pack (with dictionary). Most users choose the tiny patch; the compressed full pack is your safety net and webseed.

Legal and privacy notes for creators

You're distributing community content. Avoid including third-party copyrighted assets unless you have permission. In 2026 communities and platforms are stricter — provide clear attribution and keep a takedown policy. If you advise users on torrent clients or VPNs, present it as informational and don't instruct illegal circumvention.

Actionable checklist before release

1. Decide per-map vs bundle distribution strategy.
2. Train a zstd dictionary from previous releases if you have iterative content.
3. Repack changed assets, avoiding recompressing already-compressed files.
4. Create delta patches with xdelta3 and test apply on clean install.
5. Create torrents with appropriate piece size; include webseeds and hybrid v1/v2 metadata.
6. Publish SHA256SUMS and PGP signatures; make PAR2 files for big releases.
7. Seed with a seedbox for 48–72 hours and keep at least two seeds online long-term.

Final thoughts and future-proofing

As Arc Raiders grows in 2026 and Embark adds maps of varied scale, the community will prefer modular, patch-first distribution. Invest time in a repeatable repack and delta pipeline now: a trained dictionary, scripted repacks, and automated checks will save you bandwidth and hours of support later. The combination of zstd dictionaries + xdelta patches + smart torrent metadata is the practical sweet spot for most creators.

Call to action

If you maintain Arc Raiders maps, start by auditing your last three releases and train a zstd dictionary today. Share your test results in the community: file sizes, patch sizes, and seed strategies — and if you want, post your repo or scripts so other creators can adopt your pipeline. Want a starter script or a checklist tailored to your map size? Reply with your map's current layout and sizes and I'll draft a ready-to-run repack script you can use.

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