FEX migration between Nexus 5K and 9K

[Scott_22]

When migrating a FEX from a nexus 5k to a 9k, how long should I expect downtime to be? That is, assuming the configuration and connections have been staged beforehand. I understand that the FEX will probably download a new OS, how long does that typically take?

[Reza Sharifi]

The FEX upgrade takes about 5 minutes and that is mostly the reboot time after the upgrade.  The other thing you can do (if possible) is to connect the FEX ahead of time to the parent switch and let the parent switch upgrade the FEX. Once that is completed, attached your servers, storage, etc... This way you have the least amount of down time.

HTH