You can use the dd (data dump) command to create a backup disk drive. It will create a mirror image, which includes the partition table, of your boot disk by copying it bit by bit. In the example below, I'm using slice 2 because it represents the entire disk. Here's the syntax.
Disk to Disk (Ensure the disks are the same size)
#dd if=/dev/rdsk/c0t10d0s2 of=/dev/rdsk/c0t11d0s2 (default blocksize 512)
Blocksize is configurable (For RAIDs, we use larger blocksizes, e.g. 4k)
#dd if=/dev/rdsk/c0t10d0s2 of=/dev/rdsk/c0t11d0s2 bs=128
Disk to Tape
#dd if=/dev/rdsk/c0t10d0s2 of=/dev/rdsk/c0t11d0s2
Blocksize is configurable
#dd if=/dev/rdsk/c0t10d0s2 of=/dev/rmt/0 bs=128