DeltaSync — Intelligent File Synchronization Infrastructure

Core Engine

Every primitive for file synchronization

Built on the delta-transfer algorithm. Every flag maps to a production workflow. No abstractions — pure infrastructure.

Delta Transfer

Only transmit the differences between source and destination. The delta algorithm reduces network I/O by up to 95% on incremental syncs.

📦

Archive Mode

Preserve everything with -a: recursion, symlinks, permissions, timestamps, group, owner, and device files. One flag, total fidelity.

🗜️

Wire Compression

Compress data in-flight with -z. Negotiate zstd, lz4, or zlib automatically. Cut transfer times on slow links by 60%+.

🧹

Extraneous Purge

Remove files on the destination that no longer exist at the source with --delete. True mirror-grade synchronization.

🔒

Secure Shell Transport

Route all transfers through encrypted SSH channels with -e ssh. Zero-trust synchronization across any network boundary.

🔍

Filter Engine

Precision control with --exclude and --include patterns. CVS-mode, per-directory rules, and glob matching built in.

🧪

Dry Run

Preview every operation before execution with --dry-run. Full itemized change output without touching a single file.

📊

Progress Telemetry

Real-time transfer metrics with --progress or -P. Per-file rates, ETA, and partial-resume tracking baked into the protocol.

⏸️

Partial Resume

Interrupted transfers pick up exactly where they left off with --partial. No wasted bytes, no re-transmission. Resilient by default.

🚦

Bandwidth Control

Throttle transfer rates with --bwlimit. Run production syncs without saturating shared network links. Precision rate-limiting.

🔗

Link-Dest Snapshots

Create space-efficient backups with --link-dest. Hardlink unchanged files to previous snapshots — full history, minimal disk.

✅

Checksum Verification

Skip the quick-check and verify via 128-bit checksums with --checksum. Byte-level accuracy when correctness is non-negotiable.

Live Terminal

Watch DeltaSync in action

Real synchronization workflows. Every command authentic.

deltasync — production

$ deltasync -avz --progress /data/src/ prod:/data/dest/

sending incremental file list

config.yaml

2,048 100% 1.95MB/s 0:00:00 (xfr#1, to-chk=1247/1249)

src/api/handler.go

18,432 100% 17.58MB/s 0:00:00 (xfr#2, to-chk=1203/1249)

src/api/middleware.go

4,096 100% 3.91MB/s 0:00:00 (xfr#3, to-chk=1202/1249)

$ deltasync -avz --delete --dry-run staging:app/ /deploy/app/

receiving incremental file list

deleting old-cache/session.tmp

.d..t...... ./

>f.st...... index.html

>f+++++++++ assets/new-bundle.js

(DRY RUN) — no changes made

$ deltasync -aP --link-dest=$PWD/daily.0 prod:/ daily.1/

sending incremental file list

created directory daily.1

db/production.sqlite

524,288,000 48% 146.38MB/s 0:00:02

█

Deep Dive

The rolling checksum algorithm

How DeltaSync achieves 95%+ bandwidth reduction on incremental transfers.

Block Partitioning

The destination file is divided into fixed-size blocks. For each block, two checksums are computed: a fast rolling checksum (Adler-32 variant) and a strong hash (MD5/xxHash).

Block 1

Block 2

Block 3

Block N

Destination File → Checksums

Rolling Search

The sender slides a window across the source file byte-by-byte. At each position, the rolling checksum is compared against the hash table. Matches trigger strong-hash verification.

Source File → Rolling Window

Delta Encoding

Matched blocks become references (zero bytes transferred). Unmatched regions become literal data. The result: only the actual differences traverse the wire.

REF LITERAL REF REF LIT REF

Only literals sent → 95% savings

Capability	DeltaSync	Competitor A	Competitor B	Competitor C
Delta transfer (diffs only)	✅	❌	❌	Partial
Resumable / partial transfers	✅	❌	✅	❌
Archive-grade attribute preservation	Full (permissions, owner, group, times, symlinks)	Timestamps only	Partial	None
Filter engine (include/exclude)	✅ (glob, CVS, per-dir)	Basic glob	❌	Regex only
In-flight compression	zstd / lz4 / zlib	None	gzip	None
Bandwidth limiting	✅	❌	❌	✅
Hardlink-based snapshots	✅	❌	❌	❌
Daemon mode	✅	❌	✅	❌
Price	Free tier	$79/mo min	$49/mo min	Enterprise only

Tool

Backup strategy configurator

Generate production-ready DeltaSync commands for your backup workflow.

Backup Type

Transport

Compression

Options

Verbose -v Progress -P Delete extraneous --delete Bandwidth limit --bwlimit Dry run -n Exclude pattern Log file --log-file Checksum mode -c

Generated Command

deltasync -avz -P -e ssh /source/ user@host:/dest/

Pricing

Infrastructure that scales with you

Start synchronizing today. Upgrade when your data demands it.

Starter

$0/mo

For developers exploring sync.

-a archive mode
-v verbose output
Local transfers only
10 sync operations/day
Quick-check algorithm

Get Started

Trusted by critical operations

★★★★★

"We migrated 14TB of production data across three data centers. DeltaSync's delta algorithm meant the nightly incremental only moved 200MB. Our bandwidth costs dropped 92%."

Alexei Romanov Director of Infrastructure, NeuralGrid

★★★★★

"The --link-dest snapshot strategy revolutionized our backup pipeline. We keep 90 days of daily snapshots at the cost of one full copy. It's like having a time machine for your filesystem."

Kai Reinholt SRE Lead, DataVault Systems

★★★★★

"The dry-run + itemize-changes combination gives us complete visibility before any sync operation. In a compliance-heavy environment, DeltaSync is the only tool our security team approved."

Tobias Whitfield CISO, FinLedger Corp

★★★★★

"We deploy to 400 edge servers every release. DeltaSync's daemon mode and bandwidth limiting let us push updates without overwhelming any single link. Partial resume handles the unreliable ones."

Nadine Tanaka VP Engineering, EdgeServe

FAQ

Questions? Answers.

How does the delta-transfer algorithm actually reduce bandwidth?

DeltaSync divides the destination file into blocks and computes checksums. The source file is scanned with a rolling checksum to find matching blocks. Only the non-matching (literal) data is transmitted. For a file with a small edit, this can reduce transfer to under 1% of the file size.

Is DeltaSync secure for transferring sensitive data?

Yes. When using -e ssh, all data traverses an encrypted SSH tunnel. DeltaSync never stores credentials and supports SSH key-based authentication. For daemon mode, password files with strict permissions are supported.

What happens if a transfer is interrupted?

With --partial or -P, DeltaSync keeps partially transferred files. On the next run, it resumes from where it left off using the partial data as a basis for delta computation. Zero wasted bandwidth.

Can I preview what DeltaSync will do before it runs?

Absolutely. The --dry-run (-n) flag produces the exact same output as a real run without making any changes. Combine with --itemize-changes (-i) for a detailed per-file change manifest.

How do link-dest snapshots save disk space?

With --link-dest, DeltaSync hardlinks unchanged files from a previous backup to the new snapshot directory. Only files that actually changed consume new disk blocks. 90 daily snapshots might only use 1.5x the space of a single full copy.

Does DeltaSync work for local copies too?

Yes. DeltaSync works identically for local-to-local transfers. When both paths are local, it defaults to whole-file mode (since disk bandwidth exceeds the overhead of delta computation). Use --no-whole-file to force delta mode for testing.

Delta synchronization
infrastructure.

Every primitive for file synchronization

Delta Transfer

Archive Mode

Wire Compression

Extraneous Purge

Secure Shell Transport

Filter Engine

Dry Run

Progress Telemetry

Partial Resume

Bandwidth Control

Link-Dest Snapshots

Checksum Verification

The delta-transfer protocol

Scan

Diff

Patch

Watch DeltaSync in action

The rolling checksum algorithm

Block Partitioning

Rolling Search

Delta Encoding

Sync operations in real time

Transfer Log

Operations / min

Error Rate

The synchronization standard

Backup strategy configurator

Generated Command

Infrastructure that scales with you

Trusted by critical operations

Shipping relentlessly

zstd Compression Negotiation

xxHash-based Checksums

Incremental Recursion by Default

Questions? Answers.

Delta synchronizationinfrastructure.

Every primitive for file synchronization

Delta Transfer

Archive Mode

Wire Compression

Extraneous Purge

Secure Shell Transport

Filter Engine

Dry Run

Progress Telemetry

Partial Resume

Bandwidth Control

Link-Dest Snapshots

Checksum Verification

The delta-transfer protocol

Scan

Diff

Patch

Watch DeltaSync in action

The rolling checksum algorithm

Block Partitioning

Rolling Search

Delta Encoding

Sync operations in real time

Transfer Log

Operations / min

Error Rate

The synchronization standard

Backup strategy configurator

Generated Command

Infrastructure that scales with you

Trusted by critical operations

Shipping relentlessly

zstd Compression Negotiation

xxHash-based Checksums

Incremental Recursion by Default

Questions? Answers.

Delta synchronization
infrastructure.