xlog flus not satisfied

While doing

# VACUUM VERBOSE ANALYZE d_trr_dfh;

INFO: vacuuming "xmms.d_trr_dfh"

ERROR: xlog flush request 21F/9F57DF88 is not satisfied --- flushed only to
21F/924CE76C

CONTEXT: writing block 2919652 of relation 17461/17462/17668

I see this in the logs

user= CONTEXT: writing block 2919680 of relation 17461/17462/17668

user= WARNING: could not write block 2919680 of 17461/17462/17668

DETAIL: Multiple failures --- write error might be permanent.

user= LOG: checkpoint starting: time

xlog flush request 21F/9F67DA80 is not satisfied --- flushed only to
21F/924CE76C

Does this mean I have disk issues?

As background, this is a new box mirrored from a separate box via rsync.

I've basically copied/rsync the entire postgresql server and data files over
to create a mirror copy. After which, I've tried to do the vacuum and gotten
into the above trouble.

Any ideas from the PG community? (or is rsync not the way to go for this?)