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I've been using rsync to automatically send files from one box to another, which is great compared to scp, since it supports resuming. However, when resuming a very large file (>10gb) rsync has to read both files and compare them, which is very slow.

I don't need fancy error handling, just "scp with resume", so here's my question:

Is there an alternative to rsync/scp, that supports resuming without having to read both source and destination files?

I've read the manuals without finding anything I can use, please let me know if I've missed something. This is the rsync line I've been using:

rsync -av --partial --progress --inplace SRC DST

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up vote 6 down vote accepted

You could try the --append option of rsync since it sounds like you want to base the resumption on the sizes of the two files rather than verifying that their contents match.

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Perfect! I actually tried this before, and thought it didn't work since it still says "Sending incremental file list". However, it does not do the thorough comparison, so --append is exactly what i am looking for. Thank you! – Joernsn Apr 29 '10 at 7:22

--size-only is the switch you're looking for. It will ignore all other attributes to resume except for size, which will give you fast resume. Running rsync with this switch is pretty efficient (pretty much as efficient as scp in my experience). E.g.

rsync -rlP --append --inplace --size-only <FILES/DIRS> <dest>:<DIR>
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If you don't need comparing, only resuming you could transfer files trough FTP or HTTP.

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