February 10, 2014 at 12:56 pm
Hi All,
I always ask this question to myself very often and sometimes get confused.
Why is log shipping called a Disaster recovery solution and not a High availability solution even though it provides High availability of the database as a warm standby. Other technologies like Database mirroring and Clusterring are called High availability technologies.
Why is log shipping called a Disaster recovery solution?
Pl correct me if my statement is wrong because I heard about these terms on log shipping by lot of people.
Thanks in advance.
February 10, 2014 at 3:55 pm
they are terms which are often used in an interchangeable manner, but mirroring and clustering are better for HA because they can provide automatic failover, log shipping cannot, therefore log shipping is more often used purely for DR.
clustering is not really DR on its own because there is still the SPOF of the shared storage.
All three are often used to fulfill HA and/or DR by companies.
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February 11, 2014 at 2:30 am
Thank you very much George. 🙂
February 12, 2014 at 4:31 am
The way I see it, mirroring and clustering are considered "high availability" because they both try to maintain the standby database as an exact copy of the primary (albeit mirroring may fail in this regard due to bandwidth limitations on the links between primary and secondary). Log shipping doesn't even attempt to do that--you will always be missing however much data got put into your primary in between the last log shipping backup and the database failing, and you'll only get that data back if you can still take a tail-log backup of the primary after it fails.
February 13, 2014 at 7:32 am
Logshipping, Mirroring, Clustering and Replication (most people wouldn't use replication for HA) were all deemed High Availability technologies and provide a method of recovery using additional hardware.
There are a few terms which can be interchangeable but mean essentially the same thing. Disaster recovery, Business Continuity, High Availabilty come to mind.
All of them offerings have different benefits and limitations but it gives us as dba's great flexibility to provide a recovery method should the primary hardware fail. We have to provide a solution that fits our business constraints within the technology offered.
February 14, 2014 at 2:32 am
Thank you Paul and Jimbo.
February 24, 2014 at 12:05 pm
It's a matter of how people look at it. Some treat LS as a DR solution.
All Clustering,Mirroring,LS can be used as HA and DR solutions. As Log shipping involves moving Log Backups and shipping these backups involves some time lag, some people treat it as DR solution. Depending on RPO and RTO, even LS can be used as HA solution. Only drawback is it doesn't have automatic failover.
As per the business requirements and restrictions, one may be a better solution than other.
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SQLBuddy
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