I'm trying to to create a RAID 5 with 4x 2TB disks on Debian 6. I followed the instructions from: http://zackreed.me/articles/38-software-raid-5-in-debian-with-mdadm

I created the raid with following command: sudo mdadm --create --verbose /dev/md0 --auto=yes --level=5 --raid-devices=4 /dev/sdb1 /dev/sdc1 /dev/sdd1 /dev/sde1

After creating the RAID mdadm --detail /dev/md0 shows me:

/dev/md0:
    Version : 1.2
 Creation Time : Mon Jun 11 18:14:26 2012
 Raid Level : raid5
 Array Size : 5860535808 (5589.04 GiB 6001.19 GB)
 Used Dev Size : 1953511936 (1863.01 GiB 2000.40 GB)
 Raid Devices : 4
 Total Devices : 4
 Persistence : Superblock is persistent

Update Time : Mon Jun 11 18:14:26 2012
      State : clean, degraded
Active Devices : 3
Working Devices : 4
Failed Devices : 0
Spare Devices : 1

     Layout : left-symmetric
 Chunk Size : 512K

       Name : rsserver:0  (local to host rsserver)
       UUID : a68c3c99:1ef865e9:5a8a7bdc:64710ed8
     Events : 0

Number   Major   Minor   RaidDevice State
   0       8       17        0      active sync   /dev/sdb1
   1       8       33        1      active sync   /dev/sdc1
   2       8       49        2      active sync   /dev/sdd1
   3       0        0        3      removed

   4       8       65        -      spare   /dev/sde1

Why is there a spare drive? I didn't create one. I don't want to use a spare drive.