Amanda and LVM-based Linux installations

[Arrigo Triulzi]

Dear all,
I am trying to install a decent backup solution at a site where the 
server to be backed-up runs its filesystems over LVM (not my install, 
the LVM is actually redundant but it can't be reinstalled):

        /dev/mapper/vg1-home    197G  157G   31G  84% /home
        /dev/mapper/vg1-secure  476G   54G  398G  12% /secure
Both are ext3 filesytems:
        /dev/mapper/vg1-home on /home type ext3 (rw)
        /dev/mapper/vg1-secure on /secure type ext3 (rw)
Besides the obvious observation that the permissions of the /dev/mapper 
files are not suitable (rw for root only, nothing for group/other) I 
was wondering if there is any reason why I cannot run the Amanda client 
on it.

My plan of action is to edit /etc/lvm.conf to alter the umask parameter 
to 027 so that the /dev/mapper files are group readable.  Then I was 
planning to change them to be group "backup" so that Amanda can read 
them.

Does this make sense or am I working towards disaster?
Thanks,
Arrigo