Drives vs. Mount Points?
It depends on what's at the other end of the mount point. If the mounts are all LUNS spread across the same physical drives, then no gains. If the LUNS are all over a shared, slow, iSCSI channel, maybe no gains. If the LUNS are all under 1 controller...you see how many variables are at play. There's no one answer.

To determine the configuration of the mount points, see Locating Mount Points Using PowerShell by Boe Prox.



SQL Server has no problem with mount points. These are defined at the OS level and SQL Server "doesn't know1" they're not the same volume as the drive they appear to be mounted in.

Some Monitoring tools might give you bad information based on that last sentence, however. 

For example if you have three mount points like


C:\SQLData\SQL_Data where all your .MDB files are stored
C:\SQLData\SQL_Logs where all your .LDF files are stored
C:\SQLData\SQL_Backups where all of your .BAK and .TRN backup files are stored 


Then SQL Server will work without any issues. But if you run some sort of tool that warns you when disks are low in space, it may check the C: and not the mounted volumes below it, so you may not know when those mount points are low on disk space. Also, various "best practices" queries will throw false warnings telling you that you shouldn't have your data, logs, and backups all on the same disk because SQL Server thinks they are on the same disk. Those are false flags, and can be ignored. 

But you'd basically want to set up some additional steps in your server monitoring to make sure the C: drive has enough space and that each mount point does, too.

The times I've used mount points in SQL Server, that's been the only issue I've run into: SQL Server system health reports that give false data about free space available, and false errors saying you shouldn't have all of your data on the same drive. Since you know those are false errors, they are easy enough to ignore. 



1 SQL Server has data that makes it aware of the mount point, but from a practical use viewpoint, there's no difference in behavior. It "just works," trusting the OS to handle the specifics. Just as it trusts the OS to handle the specifics for iSCSI LUNs that are connected as local drives.