I am having FAS2040 with 12 x 600GB SAS, 56 x 2000GB SATA (DS4243) --> toal size: 116TB (toal disk: 68)
As FAS2040's tech specs said that maximum disk drives is 136 disks, maximum of capacity is 136TB, therefore, 68 disks (2TB) still available for my system but exceed fas2040's capacity, so what's happening if I use maximum disk (2TB)?
The max spindle count is the true limit - raw capacity reflects this multiplied by the biggest drive supported by a given ONTAP version.
So for ONTAP 7.3, max raw capacity is defined as 1TB x 136 disks = 136TB. For ONTAP 8.1.4 it is actually 408TB (3TB x 136).
One caveat though re max spindle count:
"To achieve the 136 max drive quantity, the FAS2040 must be configured with 4x DS424x shelves (96 drives), 2x DS14 class shelves (28 drives), and 12 internal drives. Other shelf configurations are supported within the 136 drive platform limit."