How Many NICs Per Host¶
You can use one NIC per machine. We recommend a minimum of two NICs: one for a public (front-side) network and one for a cluster (back-side) network. When you write an object from the client to the primary OSD, that single write only accounts for the bandwidth consumed during one leg of the transaction. If you store multiple copies (usually 2-3 copies in a typical cluster), the primary OSD makes a write request to your secondary and tertiary OSDs. So your back-end network traffic can dwarf your front-end network traffic on writes very easily.