It seams too be a OS thing, the best we can tell. This is usable Storage Space. Did you test your (4000) setup by removing a drive (2)? Would be recommended. Phoenix32 ran in to problems with his. But were able to correct the problem with a cable mod. His would not report a problem, failed drive.
I elected to remove my Seagate drives and run SpinRite to check the media. I have one drive that has already used 1/2 of it spare sectors used up. Hopefully with this done it will avoid the bad areas, should help the response time. It has 5 yrs to fail.
I have 400's in my 4500, After the raid 5 set was built, I only ended up with 1.09T usable space. This was with the Guardian OS. I setup with 10% SnapShot space. It may be the reason why. The doc reported the snapshots come out of the raid5 space. The GuardianOS is huge compaired to the SnapOS.
We have little to no data on the 12000. So it would be nice to have a user post some. These were advertised as 3T units. This I suspect that was with 12 x 250gig drives, 3 x 4 drive arrays, Guardian OS?. I think the early ones were 1T. Since they post the raw drive capacity and not usable numbers.
It all depends if the 1.2T limit is indeed a SnapOS limit. Does the 12000 have 6 IDE cables with the drives CS or MS? My question is how is the ide buss setup? Since yours is using the SnapOS means its one of the older units. What OS version do you have? I remember that there was a problems on loading v3 OS, v2.6 was the latest for the 12000???? I would contact snap-tech and confirm this, its a BIOS/Flashram size limit, (4m vs 8m). According to Douglas the chip can be removed on the 12000 and swapped for guardian os. At least on his engineering unit. SO if you do not have a physical copy of the flashram I'm not sure I would try a OS upgrade. I could make a backup for you if needed. Or find someone in your area and have them read the chip. This would be good info to know. It would distinguish any doubt we have about the OS. This 12000 takes a lot of $$$$ just for drives. If you have 400gig drives to test with, it would be nice to know how many the array will handle. I realize that it may take a month to build the array
, or just 2-3 days. (We have data confirming that a snap will not accept 2 750gig in raid 0, but will in raid 1. Reported a error that a number was crazy large.)
Sorry for all the questions on the 12000, but we don't see these very often. Yours is probably only the 3rd one to come through here.