Question : RAID5 over 6x 2Tb - storage limited to around 2.5Tb

Hi Guys,
I am setting up a file server/system that needs 9Tb of storage total.  The system I have decided to go with and setup has the following specs:
Gigabyte GA-EP45-UD3LR
C2D E8400 @ 3.0Ghz
6x 2Tb WD Hard Drive (all identical model)
Windows 7 Ultimate 64bit

We originally set this system up as a RAID10 with 6Tb, but now the customer needs more storage, so RAID5 is the decision.  I have created the array in Gigabyte's RAID Control panel for the motherboard, but whatever I do, I can only get about 2.5Tb total for the array.

I have added all 6 discs to the array correctly, and when I choose RAID5 it will only allow the 2.5Tb total.. I setup a partition for the OS of 250Gb thinking it might be limiting me to 2.5Tb per partition, but no luck - it would then only allow the next partition to be 2.25Tb (approx figures here).  So I created that partition and it would not allow any more as there was no room left.

Can someone please help me with this??

Thanks :)

Answer : RAID5 over 6x 2Tb - storage limited to around 2.5Tb

The deal with the rebuild is that you are exposed for data loss for a week. Lose a disk during the rebuild, and all the data is gone forever.   If you need more space, then leave it as a RAID10, and add another RAID1.  Then rebuild time will be nominal, and if you lose a disk then it will take much less time.   This may be good enough for you for now.  

Got to lsi.com and look for the SAS/SATA RAID controllers.  They have a wide range to choose from. Pretty much everybody uses LSI, or their chipsets, including IBM, HP, Dell, EMC, NetApp, Supermicro, just to name a few.    With the LSI controllers, you can go RAID6.   Also check out areca controllers.

Another benefit of RAID6 is data integrity.  If you lose a disk in RAID5, AND have a bad block (highly likely), then you lose a stripe of data.  With RAID6, you have double parity, so you can survive both a drive failure and a bad block w/o any data loss.