DO NOT REPLY [Bug 5801] New: Sparse (-S) option doesn't work with new files

[samba-bugs at samba.org]

https://bugzilla.samba.org/show_bug.cgi?id=5801

           Summary: Sparse (-S) option doesn't work with new files
           Product: rsync
           Version: 3.1.0
          Platform: Other
        OS/Version: Linux
            Status: NEW
          Severity: normal
          Priority: P3
         Component: core
        AssignedTo: wayned at samba.org
        ReportedBy: martin at scharrer-online.de
         QAContact: rsync-qa at samba.org


Excuse me, this seems to be a known issue, but I couldn't find any related
existing bug for it.

The 'handle sparse files efficiently' option (--sparse/-S) doesn't work with
new files, i.e. files with doesn't exist on the destination. In this case all
sparse blocks are transmitted as zero blocks which slows down the sync process
heavily in some application.

This issue was discussed already:
http://lists.samba.org/archive/rsync/2003-August/006998.html
http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=337827



OT:
I detected this today when I was scripting something to sync some large video
files in mkv format (around 1.1GB) with the last MB transfered first in order
to watch the incomplete video while it was transfered. (BTW: An option in rsync
for this would be awesome!!). To do this I created a sparse copy of the video
with only the last MB holding real data using 'dd if=... of=.sparse/... count=0
bs=1M seek=$SIZE_IN_MB_MINUS_ONE' and then rsyncing the .sparse dir first using
-S. To my surprise this was as slow as the rsyncing of the real file.


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