how to abort when can't write to the destination?

[Yaroslav Halchenko]

Dear Rsyncers,

I'm trying to maintain a mirror of Ubuntu distribution and I had a cron
job which rsynced it every night. The problem came after last reboot a
few days ago -- destination directory wasn't mounted, thus wasn't
accessible by rsync for writing:

rsync: failed to set times on "/share/ubumirror/.": Operation not permitted (1)
rsync: recv_generator: mkdir "/share/ubumirror/dists" failed: Permission denied (13)
rsync: stat "/share/ubumirror/dists" failed: No such file or directory (2)
rsync: recv_generator: mkdir "/share/ubumirror/dists/breezy" failed: No such file or directory (2)
rsync: stat "/share/ubumirror/dists/breezy" failed: No such file or directory (2)
rsync: recv_generator: mkdir "/share/ubumirror/dists/breezy-security" failed: No such file or directory (2)

but it kept causing all the traffic to occur and because local files
weren't present it happened to cause the transfer of a while ubuntu
mirror every night for the last few days.

I man-ed rsync but couldn't find an option which would exit rsync if any
error occurred on the way (like IO problem with destination or smth like
that)

What would be a proper way for me to set it up? (Besides piping stderr
to a process which would kill rsync if gets anything)

Please CC me - I'm not on the list

Thank you in advance for ideas!

-- 
Yaroslav Halchenko
Research Assistant, Psychology Department, Rutgers-Newark
Office: (973) 353-5440x263 | FWD: 82823 | Fax: (973) 353-1171
        101 Warren Str, Smith Hall, Rm 4-105, Newark NJ 07105
Student  Ph.D. @ CS Dept. NJIT