Using LVM in linux:

• pvcreate /dev/sdb
  Creates a Physical Volume of the whole device. Not advisable if you use other OS's that might view the device as unused.
• vgcreate DataVG /dev/sdb
  Create a Volume Group called DataVG
• lvcreate -l 90%VG -n DataLV1 DataVG
  Create a Logical Volume called DataLV1 in volume group DataVG and allocate 90% of the space in the VG to it
• mkfs.ext3 /dev/DataVG/DataLV
  Format the LV
  
  
• pvcreate /dev/sdc
  Create another PV
• vgextend DataVG /dev/sdc
  Extend the VG with the PV
• lvextend -l +50%FREE /dev/DataVG/DataLV1
  Add 50% of the free space in the VG to the LV
• resize2fs /dev/DataVG/DataLV1
  Resize the filesystem