Hi Susanta,
If Fabric Interconnect B is your subordinate you should be able to reboot it without any disruptions if fail over is up and running.I would advise to do this during a maintenance window if the need is not urgent.
You can start an SSH session into your VIP (This is the IP used to login to UCS Manager). Then run the following commands.
Show cluster extended-state (This shows which Fabric Interconnect is Primary and Secondary and if the Cluster is up and running).
Connect Local-Mgmt A/B (A or B identify's which fabric interconnect you want to connect to, if B is your subordinate that you want to reboot you would put B in this place).
Reboot (This will reboot the Fabric Interconnect).
An example of the output to do this is listed below;
TUROK-A# show cluster extended-state
Cluster Id: 0xf528a152cdc111e4-0x9bf88c604f1614a1
Start time: Wed Dec 23 13:03:34 2015
Last election time: Wed Dec 23 21:16:00 2015
A: UP, PRIMARY
B: UP, SUBORDINATE
A: memb state UP, lead state PRIMARY, mgmt services state: UP
B: memb state UP, lead state SUBORDINATE, mgmt services state: UP
heartbeat state PRIMARY_OK
INTERNAL NETWORK INTERFACES:
eth1, UP
eth2, UP
HA READY
Detailed state of the device selected for HA storage:
Chassis 1, serial: FOX1902GKT1, state: active
TUROK-A# connect local-mgmt b
Cisco Nexus Operating System (NX-OS) Software
TAC support: http://www.cisco.com/tac
Copyright (c) 2009, Cisco Systems, Inc. All rights reserved.
The copyrights to certain works contained in this software are
owned by other third parties and used and distributed under
license. Certain components of this software are licensed under
the GNU General Public License (GPL) version 2.0 or the GNU
Lesser General Public License (LGPL) Version 2.1. A copy of each
such license is available at
http://www.opensource.org/licenses/gpl-2.0.php and
http://www.opensource.org/licenses/lgpl-2.1.php
TUROK-B(local-mgmt)# reboot
