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The Benefits of Data Replication
in HACMP/PowerHA Cluster
Management Implementations
W H I T E P A P E R
Executive Summary
In today's fast-paced world, businesses both large and small face increasing internal
and external demands for data protection and efficient, uninterrupted operations. Even
a brief interruption in services and processes can have potentially disastrous results that
businesses cannot afford to risk. IT departments are being tasked with accommodating
these requirements while also being expected to do more with less in a diminishing
economy.
Fortunately, technological advances in AIX high availability, clustering disaster recovery,
and continuous operations have continually risen to meet these challenges, ensuring that
both planned outages due to maintenance and upgrades and unplanned outages due to
environmental conditions, operator error, or software bugs result in minimal data loss.
The HACMP high availability solution that clusters multiple servers to shared storage
offers automatic recovery of applications and system resources if a failure occurs with the
primary server, thereby maintaining the highest levels of data currency in that scenario.
Nonetheless, clustering is only part of the equation of a truly resilient IT infrastructure
because should the shared storage become damaged or otherwise unusable, significant
disruption of business critical applications will still occur. That is why the other essential
component of a truly resilient AIX environment is data replication technology which protects
the database by maintaining a storage clone in an offsite location. This way both servers
are redundant and storage is redundant. Still, not all replication solutions are alike.
1 v i s i o n s o l u t i o n s . c o mW H I T E P A P E R
Ensuring Protection for the Server
With the advent of globalization and of business demand for increased service-level agreements (SLAs) that require the highest level of availability of business-critical services and servers, high availability solutions became critical components in information systems-not just for large enterprises, but also for medium-sized and small businesses that, in many ways, are even more vulnerable to system outages. While a larger enterprise may have the human, technical, and financial resources to cope with and survive an unplanned outage, smaller businesses that lack similar resources can easily be put out of business if a core IT function becomes unavailable even for a short period of time.
High availability, also sometimes referred to as fault resilience, refers to technology with which servers and business services can achieve availability characteristics in the range of 99.99%-99.999%. High availability systems should be designed for businesses that can endure short periods of downtime; in contrast, fault tolerant systems are designed to achieve virtually continuous operation, albeit that level of availability requires fully redundant hardware and software components, resulting in higher solution cost.
High availability for the AIX operating system is accomplished by cost-efficiently utilizing redundant hardware and software components as well as clustering software that manages the system and is responsible for monitoring system health and performing the necessary recovery actions should a failure occur.
Since there is typically sufficient system capacity available to temporarily host services-either readily or via AIX's Capacity on Demand facility-high availability clustering will improve service availability not only during unplanned events, but also during scheduled maintenance. As high availability clustering products enable the administrator to handle system resources in groups, they can significantly improve system administration and change management practices, thereby contributing high levels of achievable service-level agreements and reducing administration labor expenses.
In order to provide high availability for AIX servers on the System p/AIX platform, IBM's high availability solution for AIX, High Availability Cluster Multi-Processing (or HACMP, now called PowerHA) has traditionally been utilized. HACMP, in its base offering, is a high availabil... [download for more]
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