Spare Hard disk is being used by other volumes

Hi Gurus,

I have a server with 2 JBOD 3300sun storege with veritas disk group datadg
configured with layer striped mirror ,Each JBOD has 1 spare disk.out of
that 1 hard disk is failing, when i try to evacuate to spare disk , it said
space is not enough though both the hard disk are same. later i found that
spare hard disk is being used by some volumes.
How should i go ahead further, pls advise.

tnx
-d