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High Availability Design Ram Dantu

High Availability Design Ram Dantu. Hi. Slides are adopted from various sources from Cisco and Interwork Inc.,. Agenda. Definitions Concepts / Calculations Examples Challenges. Availability as a percentage. 1 year = 525960 minutes. Getting downtime from availability.

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High Availability Design Ram Dantu

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  1. High Availability Design Ram Dantu Hi Slides are adopted from various sources from Cisco and Interwork Inc.,

  2. Agenda • Definitions • Concepts / Calculations • Examples • Challenges

  3. Availability as a percentage 1 year = 525960 minutes

  4. Getting downtime from availability 1 year = 525,960 minutes Uptime = availability * Time Annual Uptime = Availability * 525,960 Annual Downtime = 525,960 – Annual Uptime --------------------------------------------------------- Availability = 0.9999 Annual Uptime = .9999 * 525,960 Annual Uptime = 525,907.4 Annual Downtime = 525,960 – 525,907.4 = 52.596 ----------------------------------------------------------- Downtime = (1-Availability) * Time

  5. Availability vs. Reliability Availability = users’ perception Reliability = individual component failures Reliability impacts maintenance costs but doesn’t necessarily have to impact availability

  6. Defects Per Million

  7. MTBF Availability = MTBF + MTTR Calculating Availability Example: 6500 Chassis MTBF = 369897 hours (about 42 years) MTTR = 4 hours Availability = 369897 / ( 369897 + 4 ) = 369897 / 369901 = 0.9999892 = 99.99892%

  8. 6500 Availability

  9. A B C 99.999% 99.999% 99.999% Availability Formulas Serial availability Availability = AvailA× AvailB × AvailC = 99.999% × 99.999% × 99.999% = 99.997%

  10. A 99.9% B 99.9% Availability Formulas Parallel availability Availability = 1 – ((1 – AvailA) × (1 – AvailB)) = 1 – ((1 – 99.9%) × (1 – 99.9%)) = 99.9999%

  11. A C E 99.9% 99.9% 99.9% B D F 99.9% 99.9% 99.9% Availability Formulas Parallel-series availability   99.9999% 99.9999% 99.9999% = 99.9997%

  12. A C E 99.9% 99.9% 99.9% B D F 99.9% 99.9% 99.9% Availability Formulas Series-parallel availability 99.7% = 1 – ((1 – 99.7%) × (1 – 99.7%)) = 99.9991%

  13. Core Distribution Access

  14. One Core / Distribution 6500

  15. Pair of Core / Distribution 6500’s Series-Parallel Availability 99.99405% series availability each Two switches in parallel 1 – ((1 – 99.99405%) × (1 – 99.99405%)) = 99.999999%

  16. Access Layer 6500

  17. Challenges • Improving availability at the access layer • “NIC Teaming” in servers • Reduce MTTR MTBF = 369897 hours Availability with MTTR of 4 hours = 99.99892% Availability with MTTR of 2 hours = 99.99945%

  18. Challenges • Long convergence times • Spanning tree Eliminate layer-2 links where possible Avoid layer-2 loops Use STP enhancements where appropriate • Routing protocols Use a link-state (or EIGRP) routing protocol Use routing convergence enhancements Minimize routing table sizes Limit convergence scope

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