Speed Tips and Settings for KGB Archiver — Get Smaller Archives Fast

KGB Archiver Troubleshooting: Fix Common Errors and Recover FilesKGB Archiver is known for its extremely high compression ratios, but that often comes with increased complexity and a higher likelihood of encountering errors during compression or extraction. This guide walks you through the most common problems, how to fix them, and the steps to recover data from damaged archives. It’s written for users with basic to intermediate technical knowledge and focuses on practical, step-by-step solutions.

What is KGB Archiver?

KGB Archiver is an open-source file compression utility famous for using the PAQ compression family to achieve very high compression ratios. It supports strong compression levels that can significantly reduce file sizes, especially for redundant data, at the cost of long processing times and high memory usage. Development activity has slowed, and binaries may not be actively maintained for modern operating systems, which contributes to compatibility issues.

Before you start: important precautions

Back up original files before attempting recovery operations.
Work on copies of damaged archives, never the only existing archive.
If an archive contains critical data, consider creating a disk image of the storage medium before intensive repairs.
Be prepared: high compression levels require significant RAM and CPU time.

Common errors and quick fixes

1) “Cannot open archive” / “File format not recognized”

Cause: Corrupted header or incompatible binary.
Fixes:
- Try opening the archive with the same version of KGB Archiver that created it. If you don’t have it, search for legacy binaries for your OS (use caution and verify integrity).
- Use a hex editor to inspect the file’s signature. PAQ-based archives often have recognizable headers; compare with a healthy archive.
- If header is missing or corrupted, try header reconstruction methods (see “Repairing header damage” below).

2) Extraction fails partway through

Cause: Corrupted data blocks, insufficient memory, or file truncation.
Fixes:
- Ensure you have enough RAM / virtual memory; increase swap/pagefile.
- Try extracting on a different machine or OS with more resources.
- Use the command-line version (if available) which may give more verbose error output.
- If specific blocks are corrupt, try partial recovery (see “Partial extraction” below).

3) CRC/checksum mismatches

Cause: Data corruption, transfer errors, or disk faults.
Fixes:
- Re-download or re-transfer the archive using checksums (MD5/SHA256) to confirm integrity.
- Run disk diagnostics (chkdsk, SMART tools) if the storage medium is suspected.
- Attempt repair with archive-repair tools that can rebuild indexes or correct minor inconsistencies.

4) Very slow compression/extraction or application crashes

Cause: High compression settings, insufficient system resources, or software bugs.
Fixes:
- Use lower compression levels when creating archives; for extraction, ensure sufficient resources.
- Close other memory-intensive applications.
- Use a 64-bit build or a machine with more RAM to handle large archives.
- If application crashes, try alternate builds or command-line PAQ tools.

Repairing header damage

If the archive header is corrupted, the tool won’t recognize the archive structure. You can attempt to reconstruct or bypass the header:

Compare with a healthy KGB/PAQ archive header:
- Open a known-good archive in a hex editor and note the first few bytes (signature, version).
Replace the damaged header:
- Copy the header bytes from the healthy archive into the damaged file, then attempt opening. This works only if the damage is limited to header metadata and not the internal compressed streams.
Use a PAQ-compatible tool:
- Some PAQ-family tools can read raw compressed streams even when container metadata is damaged. Try paq8px or similar tools.
If manual editing is risky, use specialist services or forensic utilities.

Partial extraction strategies

When only parts of an archive are corrupted, you may still recover uncorrupted files:

Try listing archive contents (if the tool supports it). If listing works, extract files one-by-one — broken files will reveal themselves during extraction.
Use command-line extraction with verbose logging to identify the exact file where the process fails; then extract files after that point.
If archive uses solid compression (likely with PAQ), a single damaged block may render subsequent files unrecoverable because solid compression compresses multiple files together. In that case, recovery is more difficult; consider the approaches below.

Recovering data from truncated archives

Truncation (archive cut off early) is common after interrupted transfers or storage faults.

Use a hex editor to determine if the archive ends abruptly.
If truncation removed trailing files only, try extracting earlier files individually before the truncation point.
For PAQ-based archives, truncated compressed streams often make later data unrecoverable. However, partial recovery of initial data can still be possible.
Some advanced tools attempt brute-force reconstruction of missing end data, but success is rare and computationally expensive.

Using alternative tools and converters

Try paq8px, paq8l, or other PAQ-family implementations that may be more tolerant or updated.
Convert the archive to another format (rarely possible) only if you can extract raw streams and repack them.
If KGB Archiver was used as a GUI wrapper around PAQ engines, try running the underlying engine directly via command line.

Disk and file-system checks

If corruption is recurring, check hardware and file system:

Run SMART diagnostics on drives.
Use chkdsk / fsck on the storage medium.
Scan for bad sectors and copy data to a healthy drive using ddrescue or similar tools for failing disks.

When to seek professional help

Critical or irreplaceable data that won’t extract with the above methods.
Evidence of physical disk failure, severe corruption, or complex header damage.
Consider data recovery services or forensic specialists who can work from disk images.

Preventive measures for future archives

Use checksums (SHA256) and store them alongside archives.
Store multiple copies on different physical media.
Prefer slightly lower compression settings for important data to reduce fragility.
Keep original uncompressed copies when possible.
Test extracting backups periodically.

Example recovery workflow (concise)

Make a bitwise copy of the archive.
Verify checksum; re-download if possible.
Try opening with the same KGB version; if not, try paq8px/paq8l.
List contents; attempt single-file extracts.
If header-corrupt, compare headers and try reconstruction or use PAQ tools.
If disk issues suspected, image the disk with ddrescue and work from the image.
If all else fails, consult a recovery specialist.

Final notes

KGB Archiver can yield excellent compression but demands careful handling. Successful recovery often depends on the type and extent of corruption and the resources available. When archives hold important data, conservative practices (backups, checksums, occasional restores test) are the best defense.