Re: [Evms-cluster] is it possible to remove the cluster segment manager?

[Steve D. <st...@us...>]

be...@it... wrote on 11/25/2004 06:40:19 AM:

> Hello,
>
> we're using lvm on top of a cluster container on a external raid rack.
> We'd like to split up the cluster and remove the cluster functionality
from
> evms. Is there a way to achieve this without loosing data?
>
> thanx and regards
> Stefan

Hello, Stefan.

Unfortunately, the only way to remove the Cluster Segment Manager (CSM)
metadata from the disk(s) and preserve the data is to backup the data,
remove the CSM from the disk(s) and then restore the metadata.

The CSM puts its one sector (512 bytes) of metadata at the beginning of the
disk and puts a redundant copy at the end of the disk.  By putting its
metadata at the first sector of the disk it prevents other volume managers,
such as the DOS partitioning scheme or LVM, from thinking that they own the
disk.  The CSM gets control of the disk first and then exports the sectors
between its two metadata sectors as a separate device.  Other volume
mangers, such as DOS partitioning and LVM, can then examine the exported
device for their metadata and claim the device if they find their metadata.

If you don't have space to backup the data, you could try something risky
such as "dd bs=512 if=/dev/sda skip=1 of=/dev/sda" to move the data to the
front of the disk and then "dd bs=512 if=/dev/zero of=/dev/sda seek=<last
sector>" to erase the redundant metadata at the end of the disk.  You would
first have to make sure that all devices built from /dev/sda were
deactivated on all nodes.  I'm not sure why I mentioned that.  It sounds
way too dangerous.  But it does illustrate what needs to be done to remove
the CSM from the disk and preserve the data.

Steve D.