encrypted filesystem not encrypted?

[chris <chris@parallelsw.com>]

Hi all,

I was not sure which list to send this to, so I choose a couple that 
looked like decent fits, please advise if there is one more specific to 
the encryption.

I am currently working on a project where we are converting some of our 
filesystems to an encrypted fs using LVM2.  We are running RHEL:  
"2.6.9-55.0.2.ELsmp #1 SMP Tue Jun 12 17:59:08 EDT 2007 i686 i686 i386 
GNU/Linux"

We setup an encrypted filesystem using one of the open partitions on the 
physical hard drive using "cryptsetup create /dev/sda3"  We have 
verified this using the cryptsetup status, This shows the filesystem as 
being encrypted as aes_plain 256 bit key.  We then created an LVM and 
mounted the filesystem using the LVM.

All seems to be well, except when our testers ran the following command:
head -c 5000 /dev/sda3

They got some output that includes clear text and obviously not 
encrypted data (along with encrypted data).  Some things are date 
formatted strings like 20050912 which appears quite a few times in the 
mounted filesystem, and in the raw device (/dev/sda3).

I can post the exact commands that were used to create the filesystem, 
but they are basically
create partition ...sda3
cryptsetup create /dev/sda3 (prompts for passphrase)
pvcreate
vgcreate
lvcreate
mount

(TIA) any help (or light shed on this) is greatly appreciated!

-chris