Hello /r/sysadmin, having trouble with a server

Server boots fine with one disk,

/dev/sda1   *           1          25      200781   83  Linux
/dev/sda2              26         299     2200905   83  Linux
/dev/sda3             300        1561    10137015   82  Linux swap / Solaris
/dev/sda4            1562       60801   475845300   83  Linux

but when I add a backup drive /dev/sdb1, it fails to boot. fsck.ext3: No such file or directory....superblock

my fstab:

/dev/sda4               /                       ext3    defaults,usrquota        1 1
/dev/sda2               /tmp                    ext3    defaults        1 2
/dev/sda1               /boot                   ext2    defaults        1 2
tmpfs                   /dev/shm                tmpfs   defaults        0 0
devpts                  /dev/pts                devpts  gid=5,mode=620  0 0
sysfs                   /sys                    sysfs   defaults        0 0
proc                    /proc                   proc    defaults        0 0
/dev/sda3	        swap                   swap    defaults        0 0
/dev/sdb1		/backup			ext3	defaults	0 0

edit: the sata cables may have been switched, which I may have unswitched after reading IUseRhetoric's comment about the system switching disks. Thank you sysadmins, I feel so ashamed =(