[CentOS] Big devices and missing space

Hello,

I have a Promise EX 12-port RAID controller in my box, connected to 8 
750GB disks. I have set up 2 RAID-5 devices and joined these using LVM.

This is working fine.

However, there is something that seems wrong..
(4-1) * 750 = 2250, but df reports the LVM volume as a mere 4.0T;

/dev/mapper/storage_volume-stor  4.0T  3.6T  507G  88% /storage

Shouldn't this be 4.5TB?


Relevant bit of boot log:

scsi4 : stex
   Vendor: Promise   Model:  4 Disk RAID5     Rev: 1.10
   Type:   Direct-Access                      ANSI SCSI revision: 02
sdb : very big device. try to use READ CAPACITY(16).
SCSI device sdb: 4395053952 512-byte hdwr sectors (2250268 MB)
sdb: Write Protect is off
sdb: Mode Sense: 00 12 00 00
SCSI device sdb: drive cache: write back
sdb : very big device. try to use READ CAPACITY(16).
SCSI device sdb: 4395053952 512-byte hdwr sectors (2250268 MB)
sdb: Write Protect is off
sdb: Mode Sense: 00 12 00 00
SCSI device sdb: drive cache: write back
  sdb: sdb1
sd 4:0:0:0: Attached scsi disk sdb
sd 4:0:0:0: Attached scsi generic sg1 type 0
   Vendor: Promise   Model:  4 Disk RAID5     Rev: 1.10
   Type:   Direct-Access                      ANSI SCSI revision: 02
sdc : very big device. try to use READ CAPACITY(16).
SCSI device sdc: 4395053952 512-byte hdwr sectors (2250268 MB)
sdc: Write Protect is off
sdc: Mode Sense: 00 12 00 00
SCSI device sdc: drive cache: write back
sdc : very big device. try to use READ CAPACITY(16).
SCSI device sdc: 4395053952 512-byte hdwr sectors (2250268 MB)
sdc: Write Protect is off
sdc: Mode Sense: 00 12 00 00
SCSI device sdc: drive cache: write back
  sdc: sdc1
sd 4:0:4:0: Attached scsi disk sdc
sd 4:0:4:0: Attached scsi generic sg2 type 0
   Vendor: Promise   Model: RAID Console      Rev: 1.00
   Type:   Processor                          ANSI SCSI revision: 03
scsi 4:0:16:0: Attached scsi generic sg3 type 3

-- 
Cheers,
Morten
:wq