Thanks for the info. I install it.  I have reinstalled the OS and in OS installation partitioning step there was : a 1Mb extended partition and then the logic partition. I have deleted all and create 2 primary partition ( 1 for Os and 1 for DATA ). I have resolved.  But I don't know if  is more performing primary or logic partition. 
Good morning  [ Dell powerEdge t420, windows server 2008 R2, RAID5 ] I have attached a disk management's photo.  There's  1 extended partition wherein there is 1 logical NTFS volume that fill entirely the extended partition. But there is a green small free space of 0Mb. Is it normal ?  
Dell powerEdge t420, windows server 2008 R2, RAID5, partitioning issue