UCS 3.1(2x) to UCS 4.0(x) is a double upgrade:
- Upgrade from UCS 3.1(2x) to UCS 3.1(3latest)
- Upgrade from UCS 3.1(3latest) to UCS 4.0(4latest)
See:
https://www.cisco.com/c/en/us/td/docs/unified_computing/ucs/ucs-manager/GUI-User-Guides/Firmware-Mgmt/4-0/b_UCSM_GUI_Firmware_Management_Guide_4-0/b_UCSM_GUI_Firmware_Management_Guide_4-0_chapter_010.html
Table 5. Upgrade Paths to Release 4.0
Upgrade From Release
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Upgrade To Release
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Recommended Upgrade Path
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3.1(1), 3.1(2)
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4.0(x)
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Upgrading directly to Release 4.0(x) is not supported from this release. To upgrade to Release 4.0(x), do the following in order:
-
Upgrade the Infrastructure A bundle to Release 3.1(3) or 3.2(x).
-
Upgrade the B and C bundles for all servers to Release 3.1(3) or 3.2(x).
-
Upgrade the Infrastructure A bundle to Release 4.0(x).
|
That same doc has section:
Manage Firmware through Cisco UCS Manager
The Infrastructure (UCSM / Fabric Interconnects / IOMs) firmware upgrade can be done with the environment online, but "problems may happen" so should be done during a maintenance window.
The Server / Blade firmware upgrade will require rebooting each server, but that can be done one server at a time.
Usually an hour or two for infrastructure and about an hour per server if you do them one by one with a few reboots in between.