Span 2x2TB will not see 4TB - only 2TB

I have Windows 7 Home Premium (if that makes a difference). I recently purchased a Sans Digital MobileRaid MR2UT+ and 2x2TB Hitachi hard drives. I want to span the two drives so my computer sees a single 4TB hard drive. Problem is, when I place the two drives into the enclosure and goto Disk Management, my computer only sees 2TB total. When I pair a 160GB hard drive I had laying around with one of the 2TB, it sees and combines them. What am I doing wrong where it will not see/combine the 2x2TB?? I would appreciate any comments that could possibly help me resolve this issue. THANKS!!

It looks like it's RAIDed onboard the rack unit but could still require a BIOS update for your mobo to recognize that large of a HD. MobileRAID MR2UT+B - 2 Bay SATA to eSATA/USB 3.0 RAID 0 / 1 / JBOD / Spanning Enclosure (Black)

I'd also check to see if your BIOS supports EFI which offers more functionality for such large HD's.

Be sure to follow the unit's instructions carefully and read the entire Manual to see if you're missing anything.

2TB + 160GB is slightly less than 2 TiB. 2 TiB is where many problems begin. Are you using GPT partitioning?

gregrocker - I have the ASUS P8Z77-V Deluxe motherboard and yes, my BIOS supports EFI. You are correct - the hard drives are RAIDed onboard the enclosure. I have the silver version of the enclosure you posted the link for.

pallesenw - When I stated that I tried a 2TB and 160GB, it was only to show that the settings on the enclosure were actually working to span. It's just when I place 2x2TB in the enclosure that I only see 2TB. I was NOT using GPT partitioning. I removed both HDs and made the change to GPT and formated. When I placed them both back into the enclosure and hooked up to my rig, it still comes up as 2TB.

I know this probably has an easy solution that I'm just not seeing at the moment... if I haven't already mentioned it, I've never attempted spanning or RAID, so the answer might be "right there"... I'm just not knowledgeable enough on this topic to see it...

Check for a newer BIOS update to handle larger drives.

New hardware comes with phone, chat or email tech support that usually is hit up on these same issues regularly so may get you going faster.

gregrocker - I contacted Sans Digital Tech Support about this issue. They had me hold the reset button down for 20 seconds while booting the enclosure up. Whatever that did... it worked! Thanks for your help and suggestions.

Glad to hear it.

Let us know how that RAID enclosure works out for you, and a comparison with the drives RAIDED interally by Win7 if you ever decide to try that as well.