Problem with PITR recovery

I had a problem using PITR recovery just now. If I do:

SELECT pg_start_backup('label');
do my tar
SELECT pg_stop_backup();

and stop the server, delete /data, then recover from the tar, delete
files in pg_xlog, then set recovery.conf to restore, it fails, I think
because no actual pg_xlog file was archived since the tar.

The problem is that we don't archive the partially written xlog file,
and in this case that xlog file contains the information needed to make
the tar file consistent.

Is this a known problem? Do we document this? If so, I can't find it.

I am concerned about folks cleaning out their archive directory after
the pg_stop_backup() not realizing they need that last xlog file to make
the tar valid.

--
Bruce Momjian | http://candle.pha.pa.us
pgman(at)candle(dot)pha(dot)pa(dot)us | (610) 359-1001
+ If your life is a hard drive, | 13 Roberts Road
+ Christ can be your backup. | Newtown Square, Pennsylvania 19073