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when receiving a large file, "exporting" takes significant additional time (few minutes) #120
Description
Issue
when receiving a ~4G file there was a an "export " stage at receiving side that took multiple minutes, after the sender finished the transaction on their side
Possible cause
@matheus23 pointed out that sendme uses ExportMode::Copy from iroh-blobs, instead of other existing option, ExportMode::TryReference.
https://docs.rs/iroh-blobs/latest/iroh_blobs/api/blobs/enum.ExportMode.html
This leads to file being copied from "internal store" to target location (instead of being moved).
To confirm, I measured that on receiving file system copying the 4G file took around 7.5 minutes, which matches the previously observed delay.
Reacted by Philipp Pohl-Krüger and Ben Hagen
Activity
belkka commentedon Nov 26, 2025
Possible solution
Could
ExportMode::TryReferencebe used instead ofExportMode::Copy?Some supporting thoughts:
ExportMode::TryReferencewas used previously, but changed toExportMode::Copyin this commit. The commit message doesn't explain this specific change though, so, perhaps, it might've been accidental?ExportMode::Copymight be an immediate workaround for the bug. this fix for iroh-blobs claims to fix [BUG] directory contains files with the same hash value #103, which, perhaps, is a "real" solution, making the workaround unnecessary (?)[-]when receiving a large file, "exporting" takes significat additional time (few minutes)[/-][+]when receiving a large file, "exporting" takes significant additional time (few minutes)[/+]mrsarthi commentedon Oct 21, 2026
I looked into this, and the export mode changed from
TryReferencetoCopyin #104, which looks like the workaround for #103 (duplicate files only arriving once). @matheus23 also asked about it in #104.Now on current main, the #103 case seems fixed in iroh-blobs. With
TryReference, I sent a 2.79 GB file (on the same machine), and I sent a folder with three identical 50 MB files and two identical small files, and all five arrived as it is intact.Timing on Windows
Copy: ~108 sTryReference: ~18 sIt's a one-line change in
export(). Would you be open to a PR switching it back?