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Cisco MDS 9000: The Only High-Availability Director Switch

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The Need for High Availability in Data Center Switches

High availability is essential today, especially in industries with strict compliance and regulatory requirements such as financial and legal services and government. In an enterprise SAN, director-class switches are expected to be robust and reliable; failure to provide high availability can mean a significant loss of revenue, productivity, and reputation.


Objective of the Test

A fabric module is responsible for switching traffic across various ports on the directors. A SAN director usually has two fabric modules for high-availability, so that even if one fails, the traffic is not completely interrupted. In this document "fabric module" refers to the Fabric Module 2 for MDS 9513 Multilayer Director, to the Supervisor 2 for MDS 9506/9509 and to the Core Routing module for the competitor's 8-Gbps Director.

The test was performed to evaluate the availability of SAN directors when subject to a fabric module failure. The test simulated fabric module failure while traffic was applied through the director switch; the test then computed the frame loss and the forwarding outage time per port.

Test Setup


Test Equipment Configuration

  • Cisco MDS 9513 and 9509
    • 8-Gbps port pairs configured across two 48-port 8-Gbps modules
  • Competitor's SAN director
    • 8-Gbps port pairs configured across two 32-port modules
    • Exchange-based routing (default policy)
  • Agilent SAN Tester traffic generator
    • 99-percent load, with total traffic applied: approximately 6400 MBps

Test Procedure

  • Cisco MDS 9513
    • Power off a Fabric Module 2, remove it, and then reinsert it.
    • Remove a Fabric Module 2 without powering it off first; then reinsert it.
  • Cisco MDS 9509
    • Remove the active Supervisor 2 module without powering it off first; then reinsert it.
    • Remove the standby Supervisor 2 without powering it off first; then reinsert it.
  • Competitor's SAN director
    • Power off the Core Routing Module using the slider switch; then power it on using the slider switch.

The competitor's fabric module cannot be removed without powering it down first, so no direct removal test was performed for the competitor's director.

Results


Cisco

  • When Cisco MDS 9513 Fabric Module 2 is removed (with or without powering off)
    • No frames dropped on any port
  • When Cisco MDS 9509 (active or standby) Supervisor 2 Module is removed (with or without powering off)
    • No frames dropped on any port

Competitor

  • When Core Routing Module is turned off
    • Total frames dropped: 1,990,130
    • 0.85 second outage (the number of frames dropped divided by frames per second [fps])
  • When Core Routing Module is turned on
    • Total frames dropped: 1,626,790 after the internal diagnostics were run (about 30 seconds) and the Core Routing module was brought online
    • 0.69 second outage (the number of frames dropped divided by fps)

Real-World Application Environment

This test was repeated to observe the implications for real-world applications of the lack of high availability in the competitor's director. Instead of using the Agilent SAN Tester to generate the test data and measure the frame loss, an Oracle simulation was run, using HammerOra to generate the test data and measure the results while the Core Routing Module was turned off and on. This test allowed evaluation of the effects of frame loss at the application layer. The test configuration consisted of one server running the Oracle test script against an Oracle database on an array.