There are a number of situations which would warrant the movement of database files or transaction log files from one volume to another on the same server. These may include:
- The need to format the volume assuming it was not formatted properly when SQL Server was installed. Recall that when installing SQL Server, it is recommended that 64K allocation unit size is used to format the volumes. If this is not done at the point of installation and needs to be done later, it will obviously require preserving a backup of the database fist or creating a new, properly formatted volume and moving the database to this new volume.
- The need to use a new volume assuming the limits have been reached for the underlying storage. A good example would be the 2TB limit of a VMware Data Store. This is the case as of VSphere 5.0. Higher versions of VSphere have much higher limits.
- The need to improve performance by managing IO. One more reason you may want to move datafiles is performance. There are cases where a database is created with multiple datafiles all sitting on one disk until it becomes obvious, as the database grows, that the you have created a “hot region” in the storage layer. One solution would be creating new data files and rebuilding clustered indexes, another would be moving data files.