Thank you all for the discussion.

In the world I have right now there are only 5 drives not 6.

Considering the "D:" drive is available for SQL data, user databases

and there is the log, tempdb, backups, and "C:" drives

would you put the SQLOS , etc. on the C: drive with the OS or on the D: drive with the user databases?

The C: drive is RAID5 100GB

D: RAID10

E: RAID10

TempDB RAID10

Backups are separate and files will be backed up using Netbackup.