Hardisk 2 or more
--------------------------
It is possible to improve performance by striping(raid 0) across 2
or more disks as writes and reads will be a lot faster, but it is
not possible to improve performance if you only do mirroring
between 2 disks ie no raid.
For network interface, you can have 2 - 32 network interfaces or
more on a single machine but all of them needs to have unique IP
address, you cannot have more than 1 network interface sharing same
IP address it will crash, so to answer the question if it will
improve performance the answer is no.
When you surf internet it will only communicate using 1 network
interface, if you want to To improve network bandwidth for surfing
using 2 network interface you may need to install some special
software that will control and load balance your network traffic
between 2 nic interfaces. There are network appliance out there
currently that manage "incoming" traffic to loadbalance between a
few webservers but as far as I know it doesn't manage "outgoing"
traffic.
Also normally if a machine has more than 1 network interface is
because they want to serve more than 1 web service on the same PC
using software to create additional web instances, or they
configure that PC/server to act as a router gateway between 2
different networks or maybe that PC is a firewall gateway for many
different networks so have many n/w interface cards.
Or simply because that server is very critical that cannot afford
downtime so they install something called clustering software(very
expensive) that can detect 24/7 if the first interface goes down
the software will up other one immediately so that connection is
momentarily lost.
