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SQL Server 2008
Implementation and
Maintenance
Chapter 7: Performing Backups
and Restores
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
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Three types of data to backup
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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.
Recovery Mode
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Simple
Full
Bulk-Logged
Yes you can change a DB’s recovery model
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
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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
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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
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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
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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
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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
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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
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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
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
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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
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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
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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
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Piecemeal Restores
 Use this to restore
• The primary filegroup
• Optionally, secondary filegroups
 This lets you make part of a database
available to users
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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
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Full Backups Only
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Useful for “relatively small” databases
This is the slowest backup strategy
It has the fastest restore time
Make sure to clear t-logs manually
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Full With Differential
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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
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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
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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
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Filegroup Backups
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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
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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