Impact of moving the ldf and mdf files temporarily for few hours I want to copy my database files(ldf and mdf) into a separate box for few hours as there is a disk space issue in my current sql server box.
Currently i have mdf in one drive(:D) and ldf in another drive(:E).
I have to move both mdf and ldf into same drive,say :D.
I understand that it is recommended to have separate disk drives for LDF and MDF ,but this is a DEV box and to avoid purchase/delay client wants to go with this option.

I have two plans:


Take backups of all systems databases and user databases and save it
in a separate box.
Move MDF and LDF to a separate box for few hours


So after the partitioning/merging of disk drives are completed i can either:


Restore the backups.
Move the MDF and LDF to the merged drive.


For user database ,i understand that the below steps will be sufficient:


Bring the database offline
Move the file(s) to the new location manually.
Update the system catalog settings:

ALTER DATABASE DBNAME
        MODIFY FILE (
            NAME = 'DBNAME',
            FILENAME = 'D:\SQL_Data\DBNAME.mdf'
        )
        GO

ALTER DATABASE DBNAME
    MODIFY FILE (
        NAME = 'DBNAME_log',
        FILENAME = 'D:\SQLLog\DBNAME_log.ldf'
    )
Bring the database online


Can someone explain the dangers of second step or direct me how to do second step for system databases.?
You should don't have any issues I have done this many times before with no big issues.

One thing to consider is that if you have binaries in  E drive, you may have some issues, otherwise should be ok to go. 

From what I remember in the past you should check OS privileges, once  I had issues with the SQL Server account access to the drives. 

Another tip: If you plan to go with the move of the datafiles, you may want to try to shrink the tlog files before put offline, this way you will save some MB/GB and copy time will be faster.