Can you help me with understanding of reliability of network adapters.

Most of the time servers do have at least 2 NIC's bonded to provide sort of a HA for it. So in case of one NIC fails, the second would still do the job.

I wonder which factors work when you use network adapters.

I know that, the most important and weakest part of any computer system is: storage (i.e HDD).

but how reliable actually network adapters are?

There are more expensive ones, and cheaper adapters.

In which cases do they actually fail? In what circumstances.

1. May it be a intensive usage of them
2. Time when it's on

In your experience how often you found yourself changing NIC's due to their fail?

Or just what's the typical lifetime of commodity NIC's?

thanks.