Howto: Syncing Multi-GB CAD Assemblies (DWG / SolidWorks / STEP) Without Lock-File Corruption

Howto Guides
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Syncing engineering project directories containing multi-gigabyte CAD assemblies (SolidWorks .SLDASM, AutoCAD .DWG, Revit .rvt, and ISO 10303 STEP files) across remote workstations with rclone requires specific filter and VFS cache settings. Unlike standard document folders, CAD kernels create transient hardware lock files and incremental save buffers that cause race conditions if synced mid-session.

Here is the tested configuration we use to keep distributed CAD libraries clean on S3/B2 remotes.

1. Mandatory --filter-from Rules for CAD Lock & Backup Files

When AutoCAD, GstarCAD, or SolidWorks opens a drawing, it generates .dwl / .dwl2 who-has lock files and ~$ temporary pointers. Syncing these locks to object storage causes false "File is read-only / locked by another user" errors on peer workstations.

Create cad-filters.txt:

# AutoCAD / DWG lock and backup artifacts
- *.dwl
- *.dwl2
- *.bak
- *.sv$
- *.ac$

# SolidWorks & Inventor temporary lock files
- ~$*.SLDPRT
- ~$*.SLDASM
- ~$*.SLDDRW
- OldVersions/**

# Revit numbered local backup increments (e.g., Project.0001.rvt)
- *.[0-9][0-9][0-9][0-9].rvt
- *.[0-9][0-9][0-9][0-9].rfa

2. Preventing Partial Assembly Writes on rclone mount

Saving a top-level .SLDASM or Xref-linked .DWG triggers rapid sequential open -> write -> rename operations across dozens of sub-parts. Using --vfs-cache-mode full with a slightly extended write-back delay prevents uploading half-saved assembly states:

rclone mount s3-cad-repo:engineering-vault /mnt/cad-vault \
  --filter-from /etc/rclone/cad-filters.txt \
  --vfs-cache-mode full \
  --vfs-write-back 15s \
  --vfs-cache-max-size 100G \
  --transfers 8 \
  --checkers 16
  • Why --vfs-write-back 15s matters: CAD save routines frequently write a temporary file, verify its checksum, unlink the original, and rename the temp file within 2–5 seconds. A 15-second write-back window ensures Rclone only uploads the finalized binary after the local rename settles.
  • For estimating transfer windows and storage overhead on large 3D scene and CAD archives, you can also benchmark payload sizes with our Engineering Archive & Cloud Transfer Calculator.

Hope this saves other engineering sysadmins from chasing phantom .dwl2 lock conflicts!