High availability overview, Availability requirements, Availability evaluation – H3C Technologies H3C WX3000E Series Wireless Switches User Manual
Page 9: Mtbf, Mttr
1
High availability overview
Communication interruptions can seriously affect widely-deployed value-added services such as IPTV
and video conference. Therefore, the 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
Availability requirements
Availability requirements fall into three levels based on purpose and implementation, as shown in
Table 1 Availability requirements
Level Purpose
Implementation
1
Decrease system software and
hardware faults
•
Hardware—Simplifying circuit design, enhancing
production techniques, and performing reliability tests
•
Software—Reliability design and test
2
Protect system functions from being
affected if faults occur
Device and link redundancy and deployment of switchover
strategies
3
Enable the system to recover as fast
as possible
Performing fault detection, diagnosis, isolation, and
recovery technologies
The level 1 availability requirement should be considered during the design and production process of
network devices. The level 2 availability requirement should be considered during network design. The
level 3 availability requirement should be considered during network deployment, according to the
network infrastructure and service characteristics.
Availability evaluation
Mean Time Between Failures (MTBF) and Mean Time to Repair (MTTR) are used to evaluate the
availability of a network.
MTBF
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.
MTTR
MTTR is the average time required to repair a failed system. MTTR in a broad sense also involves spare
parts management and customer services.
- H3C WX5500E Series Access Controllers H3C WX3500E Series Access Controllers H3C WX2500E Series Access Controllers H3C WX6000 Series Access Controllers H3C WX5000 Series Access Controllers H3C LSWM1WCM10 Access Controller Module H3C LSUM3WCMD0 Access Controller Module H3C LSUM1WCME0 Access Controller Module H3C LSWM1WCM20 Access Controller Module H3C LSQM1WCMB0 Access Controller Module H3C LSRM1WCM2A1 Access Controller Module H3C LSBM1WCM2A0 Access Controller Module