rzsz不能大于4G，securefx传5.2G没有问题，
查看系统限制：
$ulimit -a
core file size (blocks, -c) 0
data seg size (kbytes, -d) unlimited
scheduling priority (-e) 0
file size (blocks, -f) unlimited
pending signals (-i) 62317
max locked memory (kbytes, -l) 64
max memory size (kbytes, -m) unlimited
open files (-n) 10000
pipe size (512 bytes, -p) 8
POSIX message queues (bytes, -q) 819200
real-time priority (-r) 0
stack size (kbytes, -s) 10240
cpu time (seconds, -t) unlimited
max user processes (-u) 102400
virtual memory (kbytes, -v) unlimited
file locks (-x) unlimited