rsync ERROR: failed verification — update discarded.

http://www.opensubscriber.com/message/rsync@lists.samba.org/2774572.html

It is telling you that the updated file that rsync created didn't match
the checksum that the sender told us. There are a number of different
ways this can happen (all of them pretty rare, but not impossible):

If this was an update (not a newly-created file):

- A block checksum may have gotten a match on some local data that
wasn't really identical, so the constructed file wasn't correct.
(The redo-pass uses a slightly different block size in order to
work-around such a rare occurrence.)

- If someone was modifying the file on the receiving side during the
interval between rsync generating the checksum data and the local
data being used to recreate the updated file, that can also cause
the end result to be incorrect (due to different data being copied
from what rsync was expecting).

For both updates and new files:

- If the sender got a read-error reading the file, the checksum is
forced to be invalid because this is the only current way rsync
has to tell the receiving side to discard the updated file.
(The observed behavior is not consistent with this possibility,
so you can ignore this one.)

- If the data being sent over the socket was corrupted (somehow), it
may be that the corruption to occurred inside the file data. This
is usually only possible with failing hardware, buggy networking
drivers, and things like that.