Disk volume not showing

Hello

My host is run hobbit 4.2 on Linux RH

On some of my machines, the DISK check, will not show all the volumes.

ie.

/dev/mapper/VolGroup00-LogVol00

/dev/cciss/c0d0p1 98747 19643 74005 21% /boot

What could be the reason for this?

Regards Lars Jensen Denmark