It's common practice to separate out the data from the log files on SQL server. Does this still hold true as best practice when working with SharePoint databases.
For example using the above example I could have my log drive have the following files:
- L:\WSS_Content_CentralAdmin.ldf
- L:\WSS_Content_MainSite.ldf
- L:\SharePoint_Config.ldf
- L:\WSS_Search.ldf
And then on my data drive have the following:
- G:\WSS_Content_CentralAdmin.mdf
- G:\WSS_Content_MainSite.mdf
- G:\SharePoint_Config.mdf
- G:\WSS_Search.mdf
Alternatively would it be more practical place each database (data and log) on it's own drive like so:
- G:\WSS_Content_CentralAdmin.mdf
- G:\WSS_Content_CentralAdmin.ldf
- H:\WSS_Content_MainSite.mdf
- H:\WSS_Content_MainSite.ldf
- I:\SharePoint_Config.mdf
- I:\SharePoint_Config.ldf
- J:\WSS_Search.mdf
- J:\WSS_Search.ldf
The other thing I want to better understand is how this advice is affected when the WSS_Content_MainSite database gets larger and we decide to add another database to the web application. Should this new database go on the same place as the other database files or in isolation?
Yes it does, for the same reasons. This posting discusses some of the issues around disk layout and storage design for SQL Server databases. A database back-end for Sharepoint has exactly the same types of issues.
Placing them on separate drives only works if they are physical on different volumes that don't sure the same spindles.
Example: IF your SharePoint server is a Dell 2950 with 6 of the 2.5 SAS drives in a raid 10. And you create the following drive partitions Then this is pointless as they share the same disks.
G:100GB H:100GB I:100GB J:100GB
Unless you have a SAN or Multiple Direct Attached Raid Devices to work with you are not going to see the benefit of splitting up the files on multiple drives.
If you do have the ability to put them on separate drives just place all of the .mdf and .ldf files like you have in your first example. This way with all the .mdf or data files on one drive they have like disk IO activity and putting all of the .ldf or log files on another drive.
Take a look at some of these articles on TechNet about Storage and DB with SharePoint. http://technet.microsoft.com/en-us/library/cc298801.aspx
Also, think about how organize your TempDB. This is very important with SharePoint.