How to fix root filesystem is full

Hello,

I  have a problem on my Netra 240 server . The root filesystem is full.

root# df -h /

Filesystem             size   used  avail capacity  Mounted on

/dev/dsk/c0t1d0s0       16G    16G    25M   100%    /

But when i run root# du -skd /  the resulte is 6481649

I think  there are hide files. How can i find them please?

I have purged lost+found files already.

root# find / -xdev -name '*' -type f -size +100000k|xargs -i ls -lrt {}

-rw-r--r--   3 root root     186777600 Apr  2  2011 /platform/sun4v/failsafe

-rw-r--r--   1 root root     59467776 Apr  7  2011 /platform/sun4v/boot_archive

-rw-r--r--   3 root root     186777600 Apr  2  2011 /platform/sun4u/failsafe