Hitachi 9900 Series User Manual

Hitachi High-Availability
Software Improves
Application Service Levels 

It is increasingly important for a business to support continued access to global

information 24 hours a day, 7 days a week. What’s more, careers often depend on the
availability of service levels provided by IT to the enterprise. 

In computer science, availability refers to the degree to which a system or resource is

capable of performing its normal function. Availability is measured in terms of Mean Time
Between Failure (MTBF) divided by MTBF plus the Mean Time to Repair (MTTR). 

•   AVAILABILITY = MTBF / (MTBF+MTTR). 

For example, a server which fails on average once every 5,000 hours and takes an

average of two hours to diagnose, replace faulty components and reboot, would have an
availability rating of 5,000/(5,000 + 2) = 99.96%. This would correspond to a Level 3
rating using the Scale of 9s. 

Many factors can cause unplanned downtime. The Hitachi Freedom Storage

™

Lightning 9900

™

has been designed to eliminate as many of these factors as possible in

both hardware redundancy, on-line replaceable components, and software data copy
functions to allow copies of data at other locations either locally or remotely so that
processing can continue in the event of an outage. 

Backup and restore procedures and products also contribute dramatically to computer

system availability by reducing the time to restore operations in the event of an outage. 

Hitachi has teamed with industry-leading storage management software providers

such as Tantian Technologies

®

and VERITAS

®

Software of Mountain View, California to

provide world-class high-availability solutions. These solutions contribute to the fact that
customers and analysts alike regard Hitachi Freedom Storage

™

systems as having the highest

availability in the industry.

The Lightning 9900

™

was designed with maximum emphasis on high-availability

computing for today’s most critical enterprises. Figure 21 highlights some of the many
advantages in high-availability design that the Lightning 9900

™

has over other enterprise

storage products. 

•   Active dual-ported disk drives instead of single-port drives or active/passive     

dual-ported drives.

•   Redundant active components throughout the system combined with automatic 

fail-over architecture.

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