SQL Server 2005 High Availability and Disaster Recovery options

Question

Hi, We are are working on a High Availability & Disaster Recovery Planning solution for an application database which is on SQL Server 2005. What different options have we got to implement this for SQL Server 2005 and after we have everything setup how
do we test the failover is working?
Thanks in advance.........
Ione

Answer 1

DR : Disaster recovery is the best option for the business to minimize their data loss and downtime. The SQL server has a number of native options. But, everything is depends upon your recovery time objective RTO and recovery point objective RPO.
1. Data center disaster
Geo Clustering
2. Server(Host)/Drive (Except shared drive) disaster
Clustering
3. Database/Drive disaster     
Database mirroring
Log shipping
Replication
Log shipping
Log shipping is the process of automating the full database backup and transaction log on a production server and then automatically restores them on to the secondary (standby) server.
Log shipping will work either Full or Bulk logged recovery model.
You can also configure log shipping in the single SQL instance.
The Stand by database can be either restoring or read only (standby).
The manual fail over is required to bring the database online.
Some data can be lost (15 minutes).
Peer-to-Peer Transactional Replication
Peer-to-peer transactional replication is designed for applications that might read or might modify the data in any database that participates in replication. Additionally, if any servers that host the databases are unavailable, you can modify the application
to route traffic to the remaining servers. The remaining servers contain same copies of the data.
Clustering
Clustering is a combination of one or more servers it will automatically allow one physical server to take over the tasks of another physical server that has failed. Its not a real disaster recovery solution because if the shared drive unavailable we cannot
bring the database to online.
Clustering is best option it provides a minimum downtime (like 5 minutes) and data loss in case any data center (Geo) or server failure.
Clustering needs extra hardware/server and it’s more expensive.
Database mirroring
Database mirroring introduced in 2005 onwards. Database Mirroring maintain an exact copy of a database on a different server. It has automatic fail over option and mainly helps to increase the database availability too.
Database mirroring only works FULL recovery model.
This needs two instances.
Mirror database always in restoring state.
http://msdn.microsoft.com/en-us/library/ms151196%28v=sql.90%29.aspx
http://blogs.technet.com/b/wbaer/archive/2008/04/19/high-availability-and-disaster-recovery-with-microsoft-sql-server-2005-database-mirroring-and-microsoft-sql-server-2005-log-shipping-for-microsoft-sharepoint-products-and-technologies.aspx
http://www.slideshare.net/rajib_kundu/disaster-recovery-in-sql-server
HADR Considerations
Need to Understand the business motivations and regulatory requirements that are driving the customer's HA/DR requirements. Understand how your customer categorizes the workload from an HA/DR perspective. There is likely to be an alignment between the needs
and categorization.
Check for both the recovery time objective (RTO) and the recovery point objective (RPO) for different workload categories, for both a failure within a data center (local high availability) and a total data center failure (disaster recovery). While RPO and
RTO vary for different workloads because of business, cost, or technological considerations, customers may prefer a single technical solution for ease in operations. However, a single technical solution may require trade-offs that need to be discussed with
customers so that their expectations are set appropriately.
Check and understand if there is an organizational preference for a particular HA/DR technology. Customers may have a preference because of previous experiences, established operational procedures, or simply the desire for uniformity across databases from
different vendors. Understand the motives behind a preference: A customers' preference for HA/DR may not be because of the functions and features of the HA/DR technology. For example, a customer may decide to adopt a third-party solution for DR to maintain
a single operational procedure. For this reason, using HA/DR technology provided by a SAN vendor (such as EMC SRDF) is a popular approach.
To design and adopt an HA/DR solution it is also important to understand the implications of applying maintenance to both hardware and software (including Windows security patching). Database mirroring is often adopted to minimize the service disruption
to achieve this objective.
HADR Options :
Failover clustering for HA and database mirroring for DR.
Synchronous database mirroring for HA/DR and log shipping for additional DR.
Geo-cluster for HA/DR and log shipping for additional DR.
Failover clustering for HA and storage area network (SAN)-based replication for DR.
Peer-to-peer replication for HA and DR (and reporting).
Backup & Restore ( DR)
keep your server DB backups in network location ( DR)
Always keep your sql server 2005 upto date, in case if you are not getting any official support from MS then you have to take care of any critical issues and more..
Raju Rasagounder Sr MSSQL DBA