Comment 6 for bug 1182094

There are a couple of issues here:

a) LSN needs to be recovered by the SST script. This is possible
, since SST script and InnoDB are not up at same time, another
instance can be spawned with --wsrep-recover. However, it would
be better if xtrabackup can made to print this (like it does with
--stats). This has another advantage that it won't require
wsrep-recover stage during normal operations as well.

b) Currently, Xtrabackup requires xtrabackup_checkpoints to be
present in datadir. This is fine, however, if and when it becomes
out of date during normal operation, the incremental apply fails.
It would be better if Xtrabackup could take --incremental-lsn (as
to_lsn in xtrabackup_checkpoints) during prepare as well.

c) Rsync SST: This has to be incremental by its nature, assuming -W is
not used, since rsync does delta transfer. Sure, it will transfer a
bit more (since it doesn't know innodb file structure), however, for
subsequent SSTs it should only transfer only the deltas.

For Xtrabackup SST, a) and b) need to be satisfied. a) can be
worked around. However, b) requires some manual adjustment or
xtrabackup should support this.

Note, this is only in the context of existing data dir. If there
is a separate prepared backup (with xtrabackup_checkpoints), it can be used for incremental SST
just fine.