Is it possible to transfer a large, dynamic file in a piecemeal fashion?

[Lars Ellenberg]

On Mon, Sep 04, 2017 at 10:45:26PM +0000, Don Kuenz via rsync wrote:
> Greetings,
>  
> Is it possible to use rsync to transmit a large, dynamic 2TB file in a 
> piecemeal fashion during daylight hours over the course of a dozen days?
> On a good day, about 200GB of data can be transferred before rsync times
> out to enable a nightly local backup to complete. The local backup
> changes a few 512 byte blocks in the 2TB file. That's why the 2TB file
> is dynamic.
> 
> As an experiment, rsync was started on the client to sync the 2TB file.
> At that point, rsyncd on the backup server created a temporarily file
> with the 2TB file name appended with a dot followed by six characters.
> 
> After about 100MB was transferred the rsync client was interrupted and
> stopped in order to simulate the nightly shutdown. When rsync was 
> restarted it erased the original 100MB temporary file and started over
> with a new, empty temporarily file. 
> 
> In summary:
> 
> * rsync apparently erases temporarily files upon restart
> 
> * it takes about a dozen days to transfer the 2TB file
> 
> Unless there's an option to have rsync pick up where it left off it
> seems impossible to transmit a large file in a piecemeal fashion. 
> Because the (nearly) same 200GB at the beginning of the 2TB file gets
> retransmitted over and over with each restart.

Would --partial work for you?
Possibly combine with --partial-dir, --temp-dir,
--delay-updates, and/or --inplace.

-- 
: Lars Ellenberg
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