How to multi-part archive creator for backup & disaster recovery
- Step 1Stage the backup set — Gather the files you're archiving onto the local machine (from a snapshot mount, vault export, or staging folder). The tool reads from disk via the File API; nothing transits the network.
- Step 2Confirm confidentiality needs — If the contents are sensitive, encrypt first with /archive-tools/encrypted-zip-creator (AES-256), since this tool does not encrypt. For an encrypt-then-split flow, split the encrypted ZIP with /archive-tools/archive-splitter.
- Step 3Generate a source checksum — Before splitting, run /archive-tools/checksum-generator to capture a SHA-256 manifest of the bundle for chain-of-custody and post-restore verification.
- Step 4Set the part size for your target — Open /archive-tools/multi-part-archive-creator, drop the files, and set Part size: 4000 for FAT32 media, 25 for email vaulting, 5–50 for retry-friendly transfers.
- Step 5Generate and store the parts — Click Generate. Download every part (archive.zip.001 …) and copy them to the off-site destination — keep all parts together; a missing one breaks reassembly.
- Step 6Verify on restore — At the recovery site, rejoin with cat archive.zip.* > archive.zip (or copy /b), unzip, then re-run the checksum generator and compare against the source manifest to confirm a clean restore.
Part sizes for backup transport targets
Type the value into the Part size field (free number, 1–4096 MB). 1 MB = 1,000,000 bytes (decimal).
| Off-site target | Part size (MB) | Constraint it respects |
|---|---|---|
| FAT32 recovery USB | 4000 | FAT32 can't store a single file ≥ 4 GiB; 4000 MB parts stay under it |
| Email vaulting / journaling | 25 | Most mailboxes cap attachments at 25 MB |
| Chunked / resumable upload | 5–50 | Smaller parts retry faster over unreliable WAN links |
| Optical media set (CD) | 650 | Fits a part per CD-R |
| Partner SFTP with per-file limit | = the limit | Match the documented per-file ceiling exactly |
What this tool does — and what it doesn't
Be precise in a DR runbook: the tool builds and splits a ZIP; it does not encrypt or split an existing archive.
| Capability | Status | Where to get it |
|---|---|---|
| Build a ZIP from local files and split by size | Yes (this tool) | — |
| Encrypt the contents | No | encrypted-zip-creator (AES-256) |
| Split an archive you already have | No | archive-splitter |
| SHA-256 manifest for verification | No | checksum-generator |
| Verify a rejoined ZIP's CRC32 | No | archive-integrity-tester |
Tier limits (archive family)
Pro-minimum tool. The size cap applies to the total bundle, not the part size.
| Tier | Max input size | Entry limit | Files per job |
|---|---|---|---|
| Pro | 500 MB | 50,000 | 20 |
| Pro + Media | 2 GB | 500,000 | 100 |
| Developer | 2 GB | 500,000 | unlimited |
Cookbook
Runbook-style snippets for splitting, transporting, and verifying a backup set. Filenames are illustrative.
Split a restore bundle for a FAT32 USB
A 6 GB-equivalent set of files won't fit FAT32 as one file. Set 4000 MB parts so each part stays under the 4 GiB single-file limit (assuming the bundle fits your tier cap).
Part size: 4000 Output parts (after level-6 ZIP): archive.zip.001 4000 MB archive.zip.002 ~1100 MB Copy both to the FAT32 stick — each part is a single sub-4 GiB file.
Encrypt, then split, then transport
This tool doesn't encrypt, so protect confidentiality first, then split the encrypted ZIP with the Archive Splitter.
1) encrypted-zip-creator → backup-aes256.zip (AES-256) 2) archive-splitter (size mode, 25 MB) → backup-aes256.zip.001 … 3) Email/transfer each part; recipient rejoins then opens with the password
Capture a verification manifest before splitting
Generate a SHA-256 manifest of the bundle so you can prove a clean restore later.
checksum-generator (SHA-256) → backup.sha256sums # After restore: $ cat archive.zip.* > archive.zip && unzip archive.zip $ sha256sum -c backup.sha256sums file1: OK file2: OK
Rejoin at the recovery site
A minimal rescue host only needs cat (or copy /b) and a ZIP extractor — both standard on modern OSes.
$ ls archive.zip.001 archive.zip.002 $ cat archive.zip.* > archive.zip $ unzip archive.zip -d /restore
Retry-friendly small parts over a flaky link
When a partner WAN link drops mid-transfer, smaller parts mean you only re-send the failed chunk.
Part size: 10 Output: archive.zip.001 … archive.zip.0NN (10 MB each) If archive.zip.007 fails to copy, re-send only that one part.
Edge cases and what actually happens
One off-site part is lost or corrupted in transit
Reassembly failsEvery part is mandatory. A raw byte split has no parity or recovery record, so a missing or corrupted middle part breaks the rejoined ZIP. Always store and verify all parts; for transport integrity, checksum each part and re-send any that fail.
Operator assumed the tool encrypts the backup
Not encryptedThis tool produces a plain ZIP split — no encryption. For confidential DR data, encrypt with encrypted-zip-creator first, then split the encrypted ZIP with archive-splitter.
You dropped an existing backup archive to re-split it
Wrong toolThis tool builds a new ZIP from local files; dropping a finished archive nests it inside another ZIP. To re-split an existing backup archive, use archive-splitter.
Bundle exceeds the tier size cap
Tier limit exceededPro caps input at 500 MB; Pro + Media and Developer at 2 GB. A large DR set may exceed even 2 GB — split it into multiple jobs, or use a streaming CLI for the build step and the Archive Splitter for slicing.
FAT32 part still too large
Adjust part sizeFAT32's hard limit is one file < 4 GiB (4,294,967,296 bytes). 4000 MB = 4,000,000,000 bytes stays safe; 4096 MB = 4,096,000,000 also fits, but leave margin. Don't set parts at or above ~4290 MB for FAT32.
Post-restore checksum mismatch
InvestigateIf sha256sum -c reports a failure after rejoin, a part was corrupted or rejoined out of order. Re-verify part order (.001 first), re-fetch the bad part, and rejoin again. Use archive-integrity-tester on the rejoined ZIP to localise CRC failures.
Already-compressed backup data
ExpectedIf the backup is mostly compressed media or existing archives, DEFLATE level 6 won't shrink it, so the part count tracks the raw size. That's normal — the value here is fitting transport limits, not extra compression.
Reassembled at a site with no extractor
SupportedModern OSes can extract ZIP natively: Windows 10+ has tar.exe and Expand-Archive; macOS and Linux have unzip/bsdtar. No special software is needed beyond the OS.
Multiple operators splitting concurrently
IndependentEach browser tab is an isolated instance with no shared state, so multiple operators can run splits at once. Tier limits apply per session.
Regulated data (HIPAA/PCI) must not leave the boundary
By designBecause processing is local and nothing is uploaded, using the tool doesn't move the regulated boundary — equivalent to running a local utility. Confirm with compliance, and add encryption + checksums for full chain-of-custody.
Frequently asked questions
Does the backup data get uploaded?
No. Files are read locally and packed by fflate WebAssembly in your browser tab; nothing is sent to a server. That's the core reason it suits sensitive DR data.
Does this tool encrypt the backup?
No. It produces a plain ZIP split. For confidential data, encrypt with the Encrypted ZIP Creator first, then split the encrypted ZIP with the Archive Splitter.
What part size fits a FAT32 recovery USB?
Use 4000 MB. FAT32 can't hold a single file ≥ 4 GiB; 4000 MB (4,000,000,000 bytes) stays safely under that ceiling.
How do I verify a restore is intact?
Capture a SHA-256 manifest with the Checksum Generator before splitting. After rejoining and extracting, run sha256sum -c against the manifest. You can also CRC-test the rejoined ZIP with the Archive Integrity Tester.
Can I split an existing backup archive?
Not with this tool — it builds a new ZIP from local files. To split an archive you already have, use the Archive Splitter.
What happens if one part is missing at restore?
Reassembly fails — a raw byte split needs every part, in order, with no recovery record. Keep all parts together and verify each one in transit.
Is this usable on a locked-down ops laptop?
Yes. It runs in the browser with no install or admin rights, which is why teams use it on managed machines where CLI tools are restricted.
What's the maximum backup size?
Pro 500 MB, Pro + Media and Developer 2 GB total input. Larger sets need multiple jobs or a streaming CLI for the build step.
How do operators rejoin parts at the recovery site?
cat archive.zip.* > archive.zip on Unix/macOS, or copy /b archive.zip.001+archive.zip.002 archive.zip on Windows, then extract the ZIP.
Does it work for HIPAA/PCI/FedRAMP data?
Local processing means the regulated boundary doesn't move. Confirm with your compliance team, and combine encryption + checksums for chain-of-custody. Treat it like running a local utility.
Can multiple analysts use it at once?
Yes — each tab is independent with no shared state. Per-session tier limits apply to each.
Why is the output not smaller than my backup?
DEFLATE level 6 barely compresses already-compressed media or existing archives. The tool's job here is splitting to fit transport limits, not deeper compression.
Privacy first
Every JAD Archive tool runs entirely in your browser using fflate, @zip.js/zip.js, and the libarchive WASM bridge. Your archives never leave your device — verified by zero outbound network requests during processing.