max file size

Matt McCutchen matt at
Thu Nov 12 23:38:48 MST 2009

On Mon, 2009-11-09 at 18:20 +0100, Heinz-Josef Claes wrote:
> Am Montag, 9. November 2009 17:48:35 schrieb Matt McCutchen:
> > On Mon, 2009-11-09 at 11:43 +0100, Heinz-Josef Claes wrote:
> > > does anybody know what's the maximum file size (terabytes?) when using
> > > rsync with options --checksum and / or --inplace?
> > >
> > > What file sizes have been tested in reality? Are there any experiences
> > > using rsync (with --checksum and / or --inplace) for big files with
> > > several / dozens or terabytes?
> > 
> > I don't believe rsync has a fixed maximum size other than "what can fit
> > in 64 bits", but I can't speak to any reliability issues that might come
> > up with extremely large files.
> > 
> I've read about a fix for overrun checksum buffers with more than some hundred 
> terabytes but that was just something undefined . . .

Indeed, I forgot about that.  The delta-transfer algorithm doesn't work
for files longer than 2^31 blocks.  With the default maximum block size
of 2^17, the limit is 2^48 bytes or 256 TB.  You could stretch the limit
by fixing a larger block size with --block-size .  See:

> > For what purpose are you considering --checksum?  In the case where the
> > file's size hasn't changed (probably true for large image files), it
> > will add an extra full read of the file on both sides before the
> > transfer begins, which would be very expensive for multi-terabyte files.
> I want to check if the following is possible:
> 1. transport a big block of data (several terabytes) physically from location 
> A to location B (very long distance) via tapes (or disks).
> (Location A and B use different storage technologies.)
> When the tapes arrive in location B, the block of data has changed in location 
> A (a program / OS is running and storing data in it).
> 2. shutdown application / OS in location A, rsync the delta between Location A 
> and B online, then restart the system in location B.
> (Perhaps step 2 has to be done multiple times.)

Since the source and destination versions are practically certain to
differ, --checksum would serve no purpose.  See the man page description
of --checksum.


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