If user's quota exceeded during backup, gzip process becomes zombie and all 4 processes (gzip, tar, sh and directadmin child) are hanged up.
Tested on FreeBSD 4.10 and 5.2.1 with DA v1.23.1
Example
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$ps l -wU indeveln
UID PID PPID CPU PRI NI VSZ RSS WCHAN STAT TT TIME COMMAND...