Intel® ICH7R South Bridge:
*4 x Serial ATA I/II 3.0Gb/s with Intel® Matrix Storage
Technology with RAID 0, 1, 5, 10 support
in Intel Matrix Storage Manager option ROM utility (Ctrl-I):
RAID 5
3x250Gb =~500 it's ok
3x1Tb = ~1800 GB
4x1Tb = ~ 764,5 GB 
Is this a limitation of the controller? or BIOS? or motherboard?
ASUS P5LD2-V - + 4x ST31000524NS
Is this a limitation of the controller?
Yes for the ICH7R and making it bootable over 2TB.
http://communities.intel.com/message/77511#77511
That would be 2TB until you get to ICH9R or higher allowing 2-256TB data volume support.
!Note that I also had to install a 64-bit version of Windows, since 32-bit versions have a 2TB per disk limit.
THANK YOU, Peter!
PS mm... and where table of max array sizes on Intel's website?
!Note that I also had to install a 64-bit version of Windows, since 32-bit versions have a 2TB per disk limit.
Note: 2TB is a hardware limitation not just a windows limitation too.
Note2: 2-256TB is possible only if its not a bootable array and windows allows 2TB+
Note3: you can only have a 2TB+ bootable array only if the hardware & windows supports it.
