It is generally recommended to put the tempdb database on disks that differ from those that are used by user databases.
I have 4 databases on my sql server, ranging from 5GB to 300GB in size.
D: drive is used for user dbs
E: drive for log files
F: drive for tempdb
Note: the drives are logical. They are not physically separate drives because they belong to SAN. Effectively this means that - based on SAN/RAID level, the data will be physically stored/spread across multiple disks. Is this a concern and going against the above recommendation?