Recommended RAID configuration for domain controller
Redundant array of independent disks (RAID) can be used for fault tolerant and to prevent single disk failures, if you have more then 1000 users accessing the domain controller then , place the log files on one RAID 1 array and keep the SYSVOL shared folder and the database together on a separate RAID 1 array.
If you have less then 1000 users accessing the domain controller then you can place all the components in a single RAID 1 array, components are OS, log files, SYSVOL, Database
Disk Space Recommendations for active directory installation
Domain controller requires available free disk space for OS, log files, SYSVOL, database.
Follow the below procedure to calculate the disk space requirement for domain controller (active directory installation)
• On the drive that will contain the Active Directory database, Ntds.dit, provide 0.4 gigabytes (GB) of storage for each 1,000 users. For example, for a forest with two domains (domain A, domain B), with 10,000 and 5,000 users respectively, provide a minimum of 4 GB of disk space for each domain controller that hosts domain A and a minimum of 2 GB of disk space for each domain controller that hosts domain B.
• On the drive containing the Active Directory log files, provide at least 500 MB of available space.
• On the drive containing the SYSVOL shared folder, provide at least 500 MB of available space. If you have more number of policy and large logon scripts then you require more then 500 MB, how ever 500 MB is minimum requirement
• On the drive containing the Windows Server 2003 operating system files, to run setup, provide at least 1.25 GB to 2 GB of available space.