Disaster is an event
that cause data loss or interface with the normal database functions.
Some of the situations of database disaster are:
Hard disk Space issues, Power failure, Virus
attack, Hardware issues, natural catastrophe etc.
Disaster recovery solution is a process to overcome data loss
after any disaster.
1.
Timely Database Backup & Restore Strategies
Daily and weekly database backup in SQL
Server and keep the backups secured.
2.
Data Replication
It is used to move the data from one server
to another server in a consistent state.
3.
Snapshot Replication
It is used to copy an entire set of data
from the publisher to the subscriber at the scheduled time.
4.
Transaction Replication
It is used to replicate data server to
server and mainly used by data warehousing and web servers.
5.
Log Shipping
It automates the backup transaction logs of
a database on the production server and restores it to the standby server at a
scheduled interval.
6.
Database Mirroring
It is suitable for high availability, high
performance data in order to increase database availability.
Always on Availability Group:
It is a high availability and disaster
recovery solution introduced in SQL Server 2012. It is used to maximize the
availability of database
Advantages:
·
It is an alternative to database mirroring
·
The main motive of Always On is to provide maximum data
availability
·
Reduced planned downtime
·
It also supports compression and encryption that
provides a high performance transport
·
It supports different types of availability group
failover like automatic, planned and forced manual failover
·
It supports two availability modes one is Asynchronous
mode and another is Synchronous mode
·
It automatically repairs page corruption
Log Shipping
The
concept of log Shipping was introduced in SQL Server 2000. It is the process of
automatically sending transaction log backup from primary database to standby
database for failover.
Failover
means replacing primary database with standby database when primary database
becomes unavailable.
There
is one primary database and one or more standby database in Log Shipping.
If
primary database fails due to some disaster then standby database is used to
restore the data.
All
activities can be recovered using log shipping such as tables, views or
permission granted etc.
It has low maintenance cost.
Replication
The concept of replication was
introduced in SQL Server 2k. It is the process of copying or distributing
database from master database to one or more other recipient databases.
Recipient database can be on same
server or different server.
Advantages
It improves availability and
scalability of data
It also maintains consistency
between databases
Using replication multiple sites can
keep copy of same data
Database Mirroring
Database Mirroring is the process of
maintaining an exact copy of SQL Server database on standby database. It works
with only those databases that use full recovery model.
Advantages
Resource consumption is very low
It increases data protection
It is reliable solution to minimize
downtime
Mirror database gets updated
automatically with production database.
It provides two ways to perform
failover one is automatic another is manual
Backup & Restore
Backup is the process of storing a
copy of database on different location so that in case of disaster data can be
restored from backup. It is the cheapest methods of recovering data.
Types:
i.
FULL Backup
ii.
DIFFERENTIAL Backup
iii.
LOG Backup
iv.
PARTIAL Backup
v.
DB Backup
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