SUMMARY: dd copy not working?

QUESTION:

I tried a dd copy from one disk to another and it appears to not have
copied over. Any suggestions??

# df -k
Filesystem            kbytes    used   avail capacity  Mounted on
/dev/dsk/c0t0d0s2    10084696 2654643 7329207    27%    /opt
/dev/dsk/c0t8d0s2    10084696  500035 9483815     6%    /optbackup

# dd if=/dev/rdsk/c0t0d0s2 of=/dev/rdsk/c0t8d0s2 bs=2048k
5000+1 records in
5000+1 records out

# df -k
Filesystem            kbytes    used   avail capacity  Mounted on
/dev/dsk/c0t0d0s2    10084696 2655213 7328637    27%    /opt
/dev/dsk/c0t8d0s2    10084696  500035 9483815     6%    /optbackup
#

SOLUTION:

Thanks for the quick responses the solution is unmount the target
filesystem!