Why High Availability
Businesses today are faced
with the critical need to ensure the availability and continuous operation of
their business systems in spite of potential failures ranging from disk crashes
and CPU failures to catastrophic losses of their computing facilities or communications
networks, and planned downtime for maintenance. Many companies also have geographically
dispersed data centers, that need information available across those data centers,
particularly when a data center has an outage, planned or unplanned.
With many companies moving
to e-commerce, it is even more critical to ensure availability. Web customers
expect businesses to be up and running all of the time. If they aren't, another
vendor or supplier is only a click away. Most of today's disaster recovery strategies
are not well suited to meet the stringent business requirements of 24 X 7 availability.
Beyond the need of mission criticality and customer expectations, any downtime
hurts the bottom line of an online business.
While solutions exist to provide
tolerance to component failure, the issue of site loss is often overlooked,
with potentially dire consequences due to business interruption and loss of
information. While off-site tape dumps have traditionally satisfied the requirements
for disaster recovery for batch systems, they are typically inadequate for protecting
the information in On-line Transaction Processing (OLTP) systems and e-business.
Asynchronous replication facilities can provide continuous duplication of critical
OLTP and e-business application information to off-site backup facilities without
the high latency inherent in tape backup strategies. Once established, such
an environment can be automated to ensure that information is replicated in
a timely manner and the switch to backup systems accomplished with minimal business
interruption. e-Businesses must provide an even higher degree of availability.
They must find a solution to provide continuous availability of their systems
or risk losing business.
High Availability should address
availability of data in three areas:
1. Manage Planned
Downtime (e.g., routine maintenance downtime, software upgrades etc.),
2. Protect during Unplanned Downtime (machine/network outages),
3. Provide Disaster Recovery. Any system providing HA services should
provide continuous availability of data in all three scenarios.
Replication Server offers data
availability in all three scenarios by providing a standby system.