1. I often see in ESXi multiple vmnics are bonded to provide redundancies. However, since UCS vnics are virtual, is it really necessary to create multiple vnics and bond them at ESXi? Does it really provide residencies and/or performance gain?
virtual vnics (defined in the service profile) are multiplexed over a hardware interface. therefore the hardware determines the bandwidth, creating multiple vnics doesn't doesn't create additional bandwidth. be also aware, that there is no vpc support between the blade and FI's.In summary, for most designs, 2 vnics and possibly 2 hbas (connecting to Fabric-A resp. Fabric-B) is enough.
2. I need to add new vnics in UCS in order to create a new vswitch in ESXi. From what I've read, adding vnics will cause the UCS blade to reboot. Is it true? Is there a way tell it not to? Also, is it required to reboot to make the new vnics visible to ESXi?
Correct ! Therefore it makes sense, to create more vnics in the service profile than you need, and let them idle. Compare this to a physical I/O adaptor, which has ports which are not connected.