[linux-lvm] Question, what is the first 384 cyclinder in the PV?

[Bryn M. Reeves]

On 07/29/2011 06:35 PM, Jewsco Pius Jacquez wrote:
> I’m sorry, I mean the first 384 sector.

It's space reserved for lvm2 data used to manage the volume; This part of the
device contains the LVM2 label and metadata area. (it's before the first
physical extent in the volume).

> I am using RHEL5.6 kernel 2.6.18-238.12.1.el5 and have lvm2-2.02.74-5.el5. Here 
> is my lvm.conf.
> 
> Can an application data exist here? Like oracle data..

Not generally but lvm2 does not necessarily write to every location in this
region when initialising a new device so if there was existing data on the
device when pvcreate/vgcreate ran it will not have been overwritten.

> For instance, if I dd out from a PV with bs=512 and count=384 and I saw oracle 
> data on it, is this ok?

It's not possible to say with this information - has oracle been configured to
use the whole disk?

If so then that's an error but if the data you are seeing is just "stale" data
from a previous use of the device it's not going to cause any problems.

Regards,
Bryn.