F3726, F3211, F3174, R5135, R3816-HP Firewalls and UTM Devices High Availability Configuration Guide-6PW100

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1BHigh availability overview
Because communication interruptions can seriously affect widely-deployed value-added services such as
IPTV and video conference, basic network infrastructures must be able to provide high availability.
The following are the effective ways to improve availability:
• Increasing fault tolerance.
• Speeding up fault recovery.
• Reducing impact of faults on services.
13B
Availability requirements
474HTable 1 describes a typical availability model that divides availability requirements into different levels.
Table 1 Availability requirements
Level Re
q
uirement Solution
1
Decrease system software and
hardware faults
• Hardware—Simplified circuit design, enhanced
production techniques, and reliability tests.
• Software—Reliability design and test.
2
Protect system functions from being
affected if faults occur
Device and link redundancy and switchover.
3
Enable the system to recover as fast
as possible
Performing fault detection, diagnosis, isolation, and
recovery technologies.
Consider level 1 availability requirements during the design and production processes of network
devices.
Consider level 2 availability requirements during network design.
Consider level 3 availability requirements during network deployment, according to the network
infrastructure and service characteristics.
14B
Availability evaluation
Mean Time Between Failures (MTBF) and Mean Time to Repair (MTTR) are used to evaluate the
availability of a network.
224BMTBF
MTBF is the predicted elapsed time between inherent failures of a system during operation. It is typically
in the unit of hours. A higher MTBF means a high availability.
225BMTTR
MTTR is the average time required to repair a failed system. MTTR in a broad sense also involves spare
parts management and customer services.