raid 5 setup on 9.10 server

[froghead]

I am puzzled as to why the size of te RAID 5 array is showing as 500GB, instead of 750GB, which is what I expected

Using ubuntu server 9.10 and would like to use raid 5.
Four disks of the same size, 300 gb.

I have created two partitions on each disk as follows:


sda1 #1 primary 250 GB B raid
#2 primary 30 GB raid

sda2 #1 primary 250 GB B raid
#2 primary 30 GB raid

sda3 #1 primary 250 GB B raid
#2 primary 30 GB raid

sda4 #1 primary 250 GB B raid
#2 primary 30 GB raid
The #1 partition on each disk was set to bootable. I then created two raid
devices. I chose three active #1 partitions from and 1 spare for each raid device. I did the same for the 4 #2 partitions.

The Partition details for the RAID devices now look as follows:


RAID5 device #0 - 500 GB Software RAID device
#1 500 GB ext4
RAID5 device #1 - 60 GB Software RAID device
#2 60 GB ext4

I was expecting the size of each of the two RAID devices to be 750GB and 90GB respectively.

Could anybody explain why the smaller size as I am reluctant to continue with the
installation until I am sure my RAID devices and partitions are setup correctly.

thanks