1. SQL Server 2008 Implementation and Maintenance Chapter 7: Performing Backups and Restores

2. Backing Up Data  A backup is a copy of your data stored in another location  There are many reasons to backup Hardware failures Natural disaster Malicious updates © Wiley Inc. 2006. All Rights Reserved.

3. Three types of data to backup  DB data  Log data  FileStream data  Important: DB data and Log data should not be on the same storage device to start, they should not be backed up to the same backup device.

4. Recovery Mode  Simple  Full  Bulk-Logged  Yes you can change a DB’s recovery model

5. How Backups Work  All backups are online backups – meaning the users can use the database while you backing up the database  SQL Server adds an LSN (log sequence number) to each log entry  SQL Server adds a checkpoint every time it writes the log to the database  The current LSN is recorded when the backup starts © Wiley Inc. 2006. All Rights Reserved.

6. How Backups Work, Cont.  The backup process is: SQL Server checkpoints the data and records the LSN of the oldest open transaction SQL Server backs up all the pages of the database that contain data © Wiley Inc. 2006. All Rights Reserved.

7. Backup Devices  Backups are stored on physical media Hard disk (local or remote) Tape drive  Backup devices tell SQL Server about the media Temporary devices are created on the fly Permanent devices are for reuse © Wiley Inc. 2006. All Rights Reserved.

8. Full Backups  This is a backup of the entire database, including: Data files and locations Portions of the transaction log  You must have a full backup before t-log and differential backups That makes this a baseline backup © Wiley Inc. 2006. All Rights Reserved.

9. Differential Backups  This records all of the changes since the last full backup  To find changes SQL Server Reads the last LSN of the last full backup Compares it with data pages Backs up the entire extent when it finds a changed page © Wiley Inc. 2006. All Rights Reserved.

10. Transaction Log Backups  Records only sections of the transaction log  This is the only backup that will clear the transaction log  If you don’t back up the log, it will fill up and users will be locked out © Wiley Inc. 2006. All Rights Reserved.

11. Filegroup Backups  VLDBs can be broken up into filegroups  Each filegroup can be backed up separately, except Tables and indexes must be backed up together if they are on separate filegroups © Wiley Inc. 2006. All Rights Reserved.

12. Other backup method  Partial Skip the read-only filegroups  Differential Partial Differential + Partial  Copy-Only Not affect the backing up sequence (no new LSN number issues) – for making a copy of production database  Mirrored

13. Using Multiple Devices  Multiple devices can speed up backups  SQL Server writes data in stripes to multiple devices in parallel All devices are written to at once  These devices become a media set  Files in a media set can’t be used individually © Wiley Inc. 2006. All Rights Reserved.

14. Restores  Backups must be restored in order Full, then differentials, then t-logs  On the last restore, use the RECOVERY option This tells SQL Server to let users back into the database © Wiley Inc. 2006. All Rights Reserved.

15. Restore Safety Checks  SQL Server records the original file locations Use the MOVE..TO option to override  It also records the original name Use the REPLACE option to override © Wiley Inc. 2006. All Rights Reserved.

16. Point-in-Time Restores  You can restore a database to a specific point in time  You must have t-log backups in place to do this  Use the STOPAT option to perform this restore © Wiley Inc. 2006. All Rights Reserved.

17. Piecemeal Restores  Use this to restore The primary filegroup Optionally, secondary filegroups  This lets you make part of a database available to users © Wiley Inc. 2006. All Rights Reserved.

18. Backup Strategy  You must have a backup strategy in place before disaster strikes  Decide what backup types you will use and when  Decide which databases to backup and when © Wiley Inc. 2006. All Rights Reserved.

19. Full Backups Only  Useful for “relatively small” databases  This is the slowest backup strategy  It has the fastest restore time  Make sure to clear t-logs manually © Wiley Inc. 2006. All Rights Reserved.

20. Full With Differential  Perform a full backup once a week or so  Perform differentials other times  This is a faster backup strategy  It takes longer to restore You have to restore more files  Make sure to clear the t-log manually © Wiley Inc. 2006. All Rights Reserved.

21. Full With T-log  Perform a full backup every night  Perform t-log backups throughout the day  This is a slower backup strategy than full/differential  It takes longer to restore than just full You have to restore more files  You get point-in-time restores  T-logs are cleared for you © Wiley Inc. 2006. All Rights Reserved.

22. Full/Differential/T-log  This is the fastest backup strategy  It is the slowest restore, but only marginally  You get point-in-time restores  The t-logs are cleared for you © Wiley Inc. 2006. All Rights Reserved.

23. Filegroup Backups  This is used for VLDBs  Perform a full backup once a month or so  Backup a filegroup once a week  Perform t-log backups throughout the day © Wiley Inc. 2006. All Rights Reserved.

24. Two new backup features for 2008  Compressed backup (4:1) Slow, not recommended, Not effective for pictures  Encrypted Need the key to decrypt Recommended to consider for the right application