Basics Of Database Administration In SQL Server: Part 6

Note: All screenshots are applied to SQL Server 2012 Enterprise Evaluation Edition.

SQL Server Storage Basics: Database Filegroups

In this part we will discuss some basic things about SQL Server File Groups. If you missed previous articles you can check them out from below link:

1. What is Filegroup

In SQL Server filegroup is a logical structure which contains objects like data file, tables and indexes. In other words we can say that a filegroup is a logical unit in which all database files are grouped together and simplifies database administration resulting into improved performance by controlling the placement of objects into specific filegroups on specific drive.
Pictorial representation of filegroups 
Figure 1: Pictorial representation of filegroups

2. Why Filegroups

Filegroups make administration easier for a DBA. Using multiple filegroups we can gain following benefits;
  1. We can separate user data with internal system data using multiple filegroups.
  2. We can overcome with maintenance overhead by putting archive (or even read-only) data onto their own filegroups and dedicated set of disks.
  3. We can gain performance improvement by putting larger tables/indexes on their own filegroup and/or dedicated set of disks.
  4. We can bring some parts of the database online quickly ( piecemeal restore ).

3. Types of Filegroups

There are two types of filegroups:
    3.1. Primary Filegroup
    3.2. User defined/Secondary Filegroup

3.1. Primary Filegroup

The filegroup which contains the primary data file and any other files that are not associated to another filegroup is termed as Primary filegroup.

3.2. User-defined Filegroup

The Filegroups which we create from FILEGROUP keyword using CREATE DATABASE or ALTER DATABASE is termed as user-defined filegroups. This file is created by user or later modifies database by a user.

4. Filegroup Examples

I am using below query to create filegroup with new database:
  3.     (NAME = N 'FG_data',  
  4.         FILENAME = N 'C:\Program Files\Microsoft SQL Server\MSSQL11.MSSQLSERVER\MSSQL\DATA\FG_data.mdf',  
  5.         SIZE = 4096 KB, FILEGROWTH = 1024 KB)  
  6. LOG ON  
  7.     (NAME = N 'FG_log',  
  8.         FILENAME = N 'C:\Program Files\Microsoft SQL Server\MSSQL11.MSSQLSERVER\MSSQL\DATA\FG_log.ldf',  
  9.         SIZE = 1024 KB, FILEGROWTH = 10 % )  
  10. GO  
  12. GO  
  15. GO  
Using above query we created database name ‘FG’ and primary filegroup which is the default filegroup and FG2 and FG3 two user-defined filegroups.

5. How to view filegroups

By executing below query we can view filegroups in a database:
  1. use FG  
  2. go  
  3. select * from sys.filegroups  
  4. go  
viewing filegroups 
Figure 2: Viewing filegroups

6. Creating a file and assigning it to filegroup

To add file in a filegroup we execute ALTER DATABASE query.
  2. ADD FILE  
  3.     (NAME = FG3_data,  
  4.         FILENAME = N 'C:\Program Files\Microsoft SQL Server\MSSQL11.MSSQLSERVER\MSSQL\DATA\FG3_data.ndf')  

7. Changing default filegroup

Again ALTER DATABASE query will execute to change the default filegroup.
Now check the default value for filegroup FG3 using sys.filegroups.
  1. use FG  
  2. go  
  3. select * from sys.filegroups  
  4. go  
Changing default filegroups 
Figure 3: Changing default filegroups
Now you can clearly see that the is_default value is 1 for FG3 filegroup. It means the default filegroup is FG3.

8. Filegroups Backup

We can take filegroups backup with two ways:
    8.1. With SQL Server Management Studio (SSMS)
    8.2. With T-SQL

8.1. With SQL Server Management Studio (SSMS)

To take backup of filegroups with ssms follow below steps:
  1. Select database>>do right click.
  2. Go to task >> click on backup,
  3. Backup database window will appear, here choose option file and filegroups under backup component.
  4. When you select file and filegroups another window will open which will show you all the filegroups for that database.
  5. Click on check boxes to take backup of one or more filegroups according to your requirement.
Step 1 and step 2
Showing how to reach backup option 
Figure 4: Showing how to reach backup option

Step 3
Choosing files and filegroups backup 
Figure 5: Choosing files and filegroups backup
Step 4 and step 5
Selecting filegroups for backup 
Figure 6: Selecting filegroups for backup

8.2. Filegroups backup with T-SQL

You can execute below query to take backup of filegroups. In below example my database name is ‘FG’ and I am taking backup of all 3 filegroups i.e.
  1. PRIMARY, FG2, FG3  
  5.     FILEGROUP = N 'FG2',  
  6.     FILEGROUP = N 'FG3'  
  7. TO  
  8. DISK = N 'C:\Program Files\Microsoft SQL Server\MSSQL11.MSSQLSERVER\MSSQL\Backup\FG.bak'  
  10. GO  
Taking filegroups backup with t-sql 
Figure 7: Taking filegroups backup with t-sql
Points to remember
  • All pages for the system tables are allocated in the primary filegroup.
  • Log files ( .ldf) does not use filegroups.
  • No file can be a member of more than one filegroup.

10. Wrap Up

In this section we discussed some basic things and saw some examples how to perform the task about filegroups which is closely related with article Basics of Database Administration in SQL Server: Part 5.
We will discuss some other points about Database storage basics in upcoming articles.
For part 7 you can click on following link: Basics of Database Administration in SQL Server: Part 7
Keep sharing your knowledge, happy reading.