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9 Dell EMC SC Series: Disaster Recovery for Microsoft SQL Server Using VMware Site Recovery Manager | CML1018
a one-hour RPO may be tied to a tier 1 SQL Server application database. This means a maximum of one
hour of data may be lost or the executed disaster recovery plan will recover data to a point within one hour or
less from the time of the disaster. RPO is improved by increasing the interval at which data is backed up or
replicated to the disaster recovery site.
1.3 Recovery time objective
Recovery time objective (RTO) is an industry-standard metric which identifies the maximum allowed recovery
time when a disaster recovery plan is executed. RTO is defined in a disaster recovery plan itself for a given
tier or data set and is subsequently used as a measurement tool to determine the success or failure of an
executed plan, whether test or actual. A variety of RTOs may exist for various tiers of applications or data
being recovered. RTO is typically measured in terms of hours or minutes. As an example, a six-hour RTO
may be tied to a tier 1 SQL Server application database. This means a maximum of six hours may elapse
from the time of the disaster until the time the SQL Server application database is made available again. The
starting point for the RTO calculation may vary between organizations but should be clearly defined in the
disaster recovery plan. As an example, the RTO calculation could be based on the precise time of the
disaster which is common for service providers, or it may be based on an organization’s formal declaration of
a disaster, rather than the disaster event itself which is the actual starting point of application and data
inaccessibility. Declaring a disaster is a process with impacts and as a result the declaration itself consumes
measurable amounts of time. The RTO calculation may or may not factor in the time required to make a
decision. RTO is generally improved by sound documentation, processes, data integrity, automation, and
virtualization.