Why does df shows only half the size of a RAID10 array?

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http://serverfault.com – I've created a RAID10 array using 4 75G drives, to create a storage of 150G. After everything finished (including the initial syncing), everything looked good except the output of df -h which showed only 73G storage on the designated mount point. Details: The machine is an m1.large Ubuntu 11.10 instance on Amazon EC2. The 4 drives are EBS drives, each is 75G in size. The RAID10 array was created using the following script: - #!/bin/sh disk1="/dev/sdh1" disk2="/dev/sdh2" disk3="/dev/sdh3" disk4="/dev/sdh4" echo "*** Verifying existence of 4 volumes $disk1, $disk2, $disk3 and $disk4" i (HowTos)