Your vmfs must have block size of at least 4MB to be able to have vmdk of 1TB, and of course you need free space in datastore.
VMFS3 Block Size choices & Volume limits:
Block Size Largest virtual disk on VMFS-3
1MB 256GB
2MB 512GB
4MB 1TB
8MB 2TB
Your vmfs must have block size of at least 4MB to be able to have vmdk of 1TB, and of course you need free space in datastore.
Block Size Largest virtual disk on VMFS-3
1MB 256GB
2MB 512GB
4MB 1TB
8MB 2TB