mount ok,but show: I/O error ,why?!

sgs

now,on my renee i can mount sgs :/test to renee:/uptest
but when :
renee#ls /uptest
show me: /uptest : I/O error?
why?
i try it many times ,get the same result
:/uptest :I/O error

(ping sgs 129.9.1.1 or ping renee 129.9.1.2 are ok)
(/uptest can be read or write)

solaris+AIX

估计硬盘有点问题