Anyone interested in compiling rtorrent for Duo V2?

Ok some initial testing. Download goes fine so far, however preallocation seems to not be working. Specifically, downloading a 700Mb file via enhanced-ctorrent (package "ctorrrent") and enabling preallocate for it (via a "-a" command line option) immediately creates a single 700Mb file, for which the following data are shown:

# filefrag -v file.mp4
File size of file.mp4 is 892549374 (217908 blocks, blocksize 4096)
 ext logical physical expected length flags
   0       0 369389568           32768
   1   32768 369422336           32768
   2   65536 369455104           32768
   3   98304 369487872           32768
   4  131072 369520640            2048
   5  133120 369524736 369522687  32768
   6  165888 369557504           32768
   7  198656 369590272           19252 eof
file.mp4: 2 extents found

ctorrent immediately allocates the entire file, before starting to download. On my old Maxtor Shared Storage II, that's how rtorrent also worked. I understood it worked that way because filefrag showed the exact same data, regardless if I run ctorrent with the preallocate option or rtorrent with the preallocate option.

Additionally, on my old platform, the files were not created with preallocation until the very first write access attempt. At that point, my rtorrent would pause for a while (probably because the preallocation routine was a blocker) and only after the file was completely created/allocated only then it would unfreeze and downloading would actually take place...

For some reason, this does not seem to be the case here, perhaps I'm missing out something. In the test file above, as time passes so does the output of filefrag changes. The extents used remain 2, but it seems that the file is heavily fragmented:

# filefrag -v file.mp4
 ext logical physical expected length flags
   0       0 369158144           30720 unwritten
   1   30720 369188864           30720 unwritten
   2   61440 369219584           30720 unwritten
   3   92160 369250304           30720 unwritten
   4  122880 369281024            2048 unwritten
   5  124928 369285120 369283071   9728 unwritten
   6  134656 369294848             101
   7  134757 369294949           27803 unwritten
   8  162560 369322752              16
   9  162576 369322768              12
  10  162588 369322780             164
  11  162752 369322944               4
  12  162756 369322948              60
  13  162816 369323008             256 unwritten
  14  163072 369323264             112
  15  163184 369323376             144 unwritten
  16  163328 369323520             198
  17  163526 369323718              10
  18  163536 369323728               5
  19  163541 369323733               3 unwritten
  20  163544 369323736             144
  21  163688 369323880               4 unwritten
  22  163692 369323884              36
  23  163728 369323920               4 unwritten
  24  163732 369323924              44
  25  163776 369323968               4
  26  163780 369323972              32
  27  163812 369324004               8 unwritten
  28  163820 369324012               5
  29  163825 369324017              15 unwritten
  30  163840 369324032              14
  31  163854 369324046            1266 unwritten
  32  165120 369325312              51
  33  165171 369325363              21 unwritten
  34  165192 369325384               6
  35  165198 369325390           13746 unwritten
  36  178944 369339136             256
  37  179200 369339392            6144 unwritten
  38  185344 369345536             349
  39  185693 369345885           27555 unwritten
  40  213248 369373440             256
  41  213504 369373696            4404 unwritten,eof
file.mp4: 2 extents found

I do know that my MSS used ext3, whereas this duo is using ext4 (not using Xraid here, just Flex-raid with JBOD). Could the preallocate function be that different in ext4?