Activating second disk on ubuntu

I have two disks installed on my ubuntu dapper machine. Each is 250GB. But only one of them appears to be mounted and usable.

root@weasel:/var/log# df -kh
Filesystem            Size  Used Avail Use% Mounted on
/dev/mapper/Ubuntu-root
                      224G   87G  125G  42% /
varrun               1007M  208K 1007M   1% /var/run
varlock              1007M  4.0K 1007M   1% /var/lock
udev                 1007M  108K 1007M   1% /dev
devshm               1007M     0 1007M   0% /dev/shm
lrm                  1007M   22M  986M   3% /lib/modules/2.6.15-26-amd64-k8/volatile
/dev/sda1             228M  102M  115M  48% /boot

Logical volume manager (LVM) has something to do with this.

root@weasel:/var/log# fdisk -l

Disk /dev/sda: 250.0 GB, 250059350016 bytes
255 heads, 63 sectors/track, 30401 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes

   Device Boot      Start         End      Blocks   Id  System
/dev/sda1   *           1          31      248976   83  Linux
/dev/sda2              32       30401   243947025    5  Extended
/dev/sda5              32       30401   243946993+  8e  Linux LVM

Disk /dev/sdb: 250.0 GB, 250059350016 bytes
255 heads, 63 sectors/track, 30401 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes

   Device Boot      Start         End      Blocks   Id  System
/dev/sdb1   *           1       30401   244196001   8e  Linux LVM

The end of the LVM Howto has some common tasks and how to do them. I noticed the pvdisplay command:

root@weasel:/etc/lvm# pvdisplay
  /dev/evms/lvm2/VolGroup00/LogVol00: read failed after 0 of 4096 at 0: Input/output error
  Couldn't find device with uuid 'Y67lyo-mEdN-F0un-yPLl-HCTa-hWLC-mCentd'.
  --- Physical volume ---
  PV Name               unknown device
  VG Name               VolGroup00
  PV Size               232.78 GB / not usable 0
  Allocatable           yes (but full)
  PE Size (KByte)       32768
  Total PE              7449
  Free PE               0
  Allocated PE          7449
  PV UUID               Y67lyo-mEdN-F0un-yPLl-HCTa-hWLC-mCentd

  --- Physical volume ---
  PV Name               /dev/sdb1
  VG Name               VolGroup00
  PV Size               232.88 GB / not usable 0
  Allocatable           yes
  PE Size (KByte)       32768
  Total PE              7452
  Free PE               2
  Allocated PE          7450
  PV UUID               mh0UHf-UYhT-NOj8-Ddlv-3NVL-hKBW-enhOXu

  --- Physical volume ---
  PV Name               /dev/sda5
  VG Name               Ubuntu
  PV Size               232.64 GB / not usable 0
  Allocatable           yes (but full)
  PE Size (KByte)       4096
  Total PE              59557
  Free PE               0
  Allocated PE          59557
  PV UUID               hzY3In-XHIh-RGwS-1ilj-nL6P-Ajts-KmySkw

There's a volume group display command as well:

root@weasel:/etc/lvm# vgdisplay
  /dev/evms/lvm2/VolGroup00/LogVol00: read failed after 0 of 4096 at 0: Input/output error
  /dev/evms/lvm2/VolGroup00/LogVol00: read failed after 0 of 4096 at 0: Input/output error
  Couldn't find device with uuid 'Y67lyo-mEdN-F0un-yPLl-HCTa-hWLC-mCentd'.
  Couldn't find all physical volumes for volume group VolGroup00.
  /dev/evms/lvm2/VolGroup00/LogVol00: read failed after 0 of 4096 at 0: Input/output error
  /dev/evms/lvm2/VolGroup00/LogVol00: read failed after 0 of 4096 at 0: Input/output error
  Couldn't find device with uuid 'Y67lyo-mEdN-F0un-yPLl-HCTa-hWLC-mCentd'.
  Couldn't find all physical volumes for volume group VolGroup00.
  Volume group "VolGroup00" doesn't exist
  --- Volume group ---
  VG Name               Ubuntu
  System ID
  Format                lvm2
  Metadata Areas        1
  Metadata Sequence No  3
  VG Access             read/write
  VG Status             resizable
  MAX LV                0
  Cur LV                2
  Open LV               2
  Max PV                0
  Cur PV                1
  Act PV                1
  VG Size               232.64 GB
  PE Size               4.00 MB
  Total PE              59557
  Alloc PE / Size       59557 / 232.64 GB
  Free  PE / Size       0 / 0
  VG UUID               85vnO6-FtRR-SZnS-s0UQ-aFNf-OY5X-ZiwMm0