rsync hints for heterogenous environments, especially [V]FAT

Unfortunately sometime one has to rsync directories between too different filesystems.
E.g., [V]FAT[32] which is widely used on USB sticks and external hard drives, has a 2-second granularity for timestamps and does not support unix's owner+group system.

Here are the rsync options that can make one's life much easier in such situations:

--modify-window=2
... increases the granularity of timestamp comparisons (actually =1 should do) and avoids very much unneccessary traffic at the second run and any further run.
Btw., rsync really should detect such situations automatically, at least locally.

--no-owner --no-group
... suppresses error messages meaningless on FAT respectively.
It's also recommended on SMBFS/CIFS and NTFS, because those know owner attributes but usually use different user+group databases.

From: IBCL BLog.
Originally posted: 2008-07-19