title: rsync suddenly hanging indefinitely during transfers
body: <p>For the past few years, I have been using an rsync one-liner to back up important folders on my Mac Mini desktop (OSX 10.9, 2.5 GHz i5, 4 GB RAM) to a FreeNAS box (0.7.2 Sabanda revision 5266, Pentium D 2.66 GHz, 822MiB RAM [reported by the system, I think there's 1 GB in there]). I am running an rsync daemon on the FreeNAS box. Recently, these transfers have been hanging indefinitely. I have done the usual Google-fu and am unable to identify the source of the problem or a solution.</p>
  
  <p>The one-liner is:</p>
  
  <pre class="lang-sh prettyprint-override"><code>rsync -rvOlt --exclude '.DS_Store'                                  \
        --exclude '.com.apple.timemachine.supported'                  \
        --delete /Volumes/Storage/Music/Albums/ 192.168.1.100::albums
  </code></pre>
  
  <p>I have tried enabling <code>-vvv</code> and <code>--progress</code>, but there is no pattern that I can discern between what hangs and what doesn't. Heck, if I retry, the same file might hang at a different point during the transfer or not at all. A dry run (<code>-n</code>) does not always succeed either. The only "success" I've had is implementing a timeout (<code>--timeout=10</code>) and rerunning the command over and over. Eventually, I creep along, but with no guarantee of success and at a pace that is unacceptable. I've reached a point where I have one file that I can't get past.</p>
  
  <p>The Mac Mini is connected to my router via 5 GHz. The FreeNAS box is wired into that same router on a 100 mbit port. When transfers are actually going, <code>rsync --progress</code> reports 2.5-4 MB/s. According to <code>--progress</code>, a hang is literally just that—no data transfer is occurring as far as I can tell.</p>
  
  <p>I need help with both the diagnostics and the solution.</p>