Bài giảng Cơ sở dữ liệu nâng cao Chapter 2 Disaster recovery

Bài giảng Cơ sở dữ liệu nâng cao Chapter 2 Disaster recovery. Chương này trình bày một số nội dung sau Overview about database backup and recovery, backup restore strategy, disaster recovery planning,... Mời các bạn cùng tham khảo.

CHAPTER 2

Disaster Recovery

Agenda

Overview about database backup and recovery

information about its customers, inventory, purchases,

financials, and products

Anything from a user error to a natural disaster could take your database offline Your backup and recovery plan

needs to account for the possibility of these failures and more

Overview about database backup and recovery

• Media failure.

• User errors, for example, dropping a table by mistake.

• Hardware failures, for example, a damaged disk drive or permanent loss of a server.

• Natural disasters.

Overview about database backup and recovery

to enable you to recover a damaged database

maximizes data availability and minimizes data loss, while considering your particular business requirements.

Backup & restore strategy

• The backup strategy defines:

• The type and frequency of backups

• The nature and speed of the hardware that is required for them

• How backups are to be tested

• Where and how backup media is to be stored (including security considerations)

Backup & restore strategy

• The restore strategy defines:

• Who is responsible for performing restores

• How restores should be performed to meet the goals

• for availability of the database

• for minimizing data loss

• Designing an effective backup and restore strategy requires careful planning, implementation, and testing

Backup method

• Database Engine provides four different backup methods:

• Full database backup

• Diferential backup

• Transaction log backup

• File (or filegroup) backup

Backup method

• Full database backup:

• Capture the state of the database at the time the backup is started

• During the full database backup, the system copies the data, the schema of all tables of the database and the corresponding file structures

• Even all uncommitted transactions in the

transaction log are written to the backup media.

Backup method

• Differential Backup

• Create a copy of only the parts of the database that have changed since the last full database backup

• The advantage of a differential backup is speed It minimizes the time required to back up a database.

Backup method

• Transaction Log Backup:

• Consider only the changes recorded in the log This form of backup is therefore not based on physical parts (pages) of the database, but rather on logical operations - that is, changes executed using the

DML statements INSERT, UPDATE, and DELETE Again, because the amount of data is smaller, this process can be performed significantly quicker than

a full database backup and quicker than a

differential backup.

Backup method

• File or Filegroup Backup:

of the entire database

database backup, allowing recovery from a failure that affects only a small subset of the database files

backup to restore individual files or filegroups This

means that you can use database and transaction log backups as your backup procedure and still be able to restore individual files (or filegroups) from the database backup

Recovery model

SQL Server database or individual files or filegroups of the database Table-level backups cannot be created

• Simple

• Full

• Bulk Logged

meant for regular use Bulk Logged,is designed to be an adjunct to the Full recovery model

Recovery model

log, because the transaction log is not backed up

the lost data

Recovery model

• All activities that affect the database are logged in the transaction log.

• The advantage of this full logging is that every transaction can be recovered in the event of a failure.

Recovery model

• Log most bulk operations

• For certain large-scale bulk operations such as bulk import or index creation, switching temporarily to the bulk-logged recovery model increases performance and reduces log space consumption.

Backup Types

whole database, a partial database, or a set of files or filegroups

• Full backup

• Differential backup

• Transaction log backup

Backup Types

• Contain all the data in a specific database or set of filegroups or files, and also enough log to allow for recovering that data.

• based on the latest full backup of the data.

• Contain only the data that has changed since the differential base.

• In Full or Bulk-Logged recovery models