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How to perform VCS Fabric Multi-Version Upgrade

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TitleHow to perform VCS Fabric Multi-Version Upgrade
Objective
Provide an update on the current methodology that significantly reduces the time to upgrade a VCS Logical Chassis Fabric.

 
Environment
  • The standard and best practice approach to upgrading a fully redundant spine/leaf Extreme Networks VCS Logical Chassis Fabric is to upgrade the fabric in an Odd/Even manner. 
  • A fully redundant VCS fabric is one where the fabric is composed of VDX switches in a spine/leaf configuration and all connected hosts have redundant connections to the leaf switches. The leaf switches are redundantly connected to the spine switches and the spine switches are connected to each other. 
  • A host device, in such a fabric has two paths by which data can enter and leave the host and if one path is unavailable the host has another path to send/receive data.  This redundancy ensures that traffic disruption is kept to a minimum when a redundant switch is down due to a fault or a scheduled maintenance event.
  • Below shows the topology of a fully redundant host network
Figure A
 
topology of a fully redundant host network
Procedure

Extreme Networks VCS Fabric Upgrade Methodology

The "odd/even" method is one where the fabric is split equally into odd and even nodes that represent both sides of the redundant traffic path. This "odd/even" grouping does not include the principle switch which is upgraded last in a separate group.

Because of the built-in redundancy, both groups (either all odd or all even) have traffic connectivity to all hosts and end devices during the upgrade process. As a result, reloading any one group results in minimal traffic loss. Table A shows the groupings for the redundant fabric shown in Figure A in environment section.
Table A.
GroupRbridge ID
Even2,4,6
Odd3,5
Principle Switch1
Table B. Shows the timing in Hours:Minutes per group for a three version upgrade for the Figure A fabric using the "Odd/Even" best practice. 
Table B.
Upgrade
Version
GroupTime
1Odd0:30
Even0:30
Principle Switch0:45
2Odd0:30
Even0:30
Principle Switch0:45
3Odd0:30
Even0:30
Principle Switch0:45
Total5:15
There are multitude of tasks to be performed in a maintenance window of which one aspect is the actual upgrading of the fabric.  Five plus hours is a long time to spend just upgrading the fabric and it makes you wonder if there is a method by which the time required to upgrade a fabric can be reduced and still provide the same benefits as the "Odd/Even" method.

Extreme Networks has developed the Multi-Version Upgrade Methodology to address this need. 

[(Continued in Additional Notes: )]

Additional notes

Extreme Networks VCS Fabric Upgrade Multi-Version Upgrade Methodology

The VDX's has the ability to download its configuration from the Principal switch when that switch is replaced or has its configuration defaulted before being re-introduced into the fabric. The Multi-Version Upgrade methodology was developed around this specific capability.
More specifically, the  Multi-Version Upgrade Methodology (MV) is where a temporary Principal switch is upgraded, one version at a time, from its initial version to its target version and the rest of the fabric is upgraded, from its initial version to its target version in one pass using the "firmware download default-config" command. The use of the default-config option triggers the VDXs to download their configurations from the Principal switch. 

The temporary Principal switch can be an existing leaf switch or an additional switch which is temporarily added to the fabric.

Table C. Show the timing for a three version upgrade for the Figure A Fabric using the Multi-Version Methodology with the "Odd/Even" best practice.
Table C.
Upgrade
Version
GroupTime
1Temporary Principle Switch0:30
2Temporary Principle Switch0:30
3Temporary Principle Switch0:30
Odd0:45
Even0:45
Total 3:00
In this example the Multi-Version Upgrade Methodology reduces the upgrade time for the six-node fabric by two hours and 15 minutes.  Table D shows the time savings per number of versions required for the upgrade. 
Table D.
Upgrade
Versions
TraditionalMulti-VersionSavings
35:153:002:15
47:003:303:30
58:454:004:45
610:304:306:00
The table indicates that there can be a significant savings can be realized when a large number of versions need to be applied during a maintenance window.

Click on the following link for complete details. NOS Multi-Version White Paper

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