LVM mount physical disk for backups

Question

I have a home server running Centos 6.4. There are 2 400GB physical disks, and I believe I have 1 logical volume over one of the disks. I want to mount the 2nd disk under /backup and use it for backups only (my thinking was to keep backup data on a separate physical device).

1. Are my assumptions about my set up correct?
2. Should I add the 2nd disk to the LVM, and if so how do I ensure that only backup data goes to the 2nd disk?
3. Should I the disk some other way

I've included some paired down output that I hope will be useful:

[root@server ~]# fdisk -l

Disk /dev/sda: 400.1 GB, 400088457216 bytes
...

   Device Boot      Start         End      Blocks   Id  System
/dev/sda1   *           1          64      512000   83  Linux
Partition 1 does not end on cylinder boundary.
/dev/sda2              64       48642   390198272   8e  Linux LVM

Disk /dev/sdb: 400.1 GB, 400088457216 bytes
...

   Device Boot      Start         End      Blocks   Id  System
/dev/sdb1               1       48642   390710272   83  Linux

Disk /dev/mapper/vg_server-lv_root: 53.7 GB, 53687091200 bytes
... 

Disk /dev/mapper/vg_server-lv_swap: 8405 MB, 8405385216 bytes
...

Disk /dev/mapper/vg_server-lv_home: 337.5 GB, 337469505536 bytes
...

[root@server ~]# df -H
Filesystem             Size   Used  Avail Use% Mounted on
/dev/mapper/vg_server-lv_root
                        53G   3.5G    47G   7% /
tmpfs                  4.2G      0   4.2G   0% /dev/shm
/dev/sda1              508M    68M   415M  14% /boot
/dev/mapper/vg_server-lv_home
                       333G    41G   275G  13% /home

[root@server ~]# pvs --all
  PV                     VG        Fmt  Attr PSize   PFree
  /dev/ram0                             ---       0     0
  /dev/ram1                             ---       0     0
  /dev/ram10                            ---       0     0
  /dev/ram11                            ---       0     0
  /dev/ram12                            ---       0     0
  /dev/ram13                            ---       0     0
  /dev/ram14                            ---       0     0
  /dev/ram15                            ---       0     0
  /dev/ram2                             ---       0     0
  /dev/ram3                             ---       0     0
  /dev/ram4                             ---       0     0
  /dev/ram5                             ---       0     0
  /dev/ram6                             ---       0     0
  /dev/ram7                             ---       0     0
  /dev/ram8                             ---       0     0
  /dev/ram9                             ---       0     0
  /dev/root                             ---       0     0
  /dev/sda1                             ---       0     0
  /dev/sda2              vg_server lvm2 a--  372.12g    0
  /dev/sdb1                             ---       0     0
  /dev/vg_server/lv_home                ---       0     0
  /dev/vg_server/lv_swap                ---       0     0

Edit

Further output as requested

[root@server ~]# cat '/proc/partitions'
major minor  #blocks  name

   8        0  390711384 sda
   8        1     512000 sda1
   8        2  390198272 sda2
   8       16  390711384 sdb
   8       17  390710272 sdb1
 253        0   52428800 dm-0
 253        1    8208384 dm-1
 253        2  329560064 dm-2

Answer 1

You appear to have 3 logical volumes: root, /home, and swap. There's no reason to add the backup drive to LVM. If you do, then you can specify which disk a volume should be allocated on when you create it, though in your case, your first disk is already 100% allocated, so the new disk is the only place a new volume could go.