When configuration php-fpm you are able to configure it using ports or sockets.
The best thing to do is configure with socks as this avoids the networking stack associated with ports.
This means that php-fpm will be using files (sockets) to run which could be considered slower because of potential slow HDDs however the files are mostly stored in RAM so it makes accessing them significantly quicker.

CentOS 6 uses FHS 2.3, this means that it uses /dev/shm for accessing RAM

You can see from the output below the tmpfs (temporary file system) is mounted to /dev/shm:

# df -h
Filesystem      Size  Used Avail Use% Mounted on
/dev/sda2       1.8T  194G  1.6T  12% /
tmpfs           1.9G  4.0K  1.9G   1% /dev/shm
/dev/sda1       190M   88M   93M  49% /boot

To specify different server pools for each website you can create a website pool in the /etc/php-fpm.d/ directory.
E.g /etc/php-fpm.d/lukeslinux.co.uk
You would then want something similar to the following:

[lukeslinux.co.uk]

listen = /dev/shm/php-fpm-lukeslinux.co.uk.sock
listen.allowed_clients = 127.0.0.1

user = nginx
group = nginx

pm = dynamic
pm.max_children = 50
pm.start_servers = 5
pm.min_spare_servers = 5
pm.max_spare_servers = 35

slowlog = /var/log/php-fpm/lukeslinux.co.uk-slow.log

php_admin_value[error_log] = /var/log/php-fpm/lukeslinux.co.uk-error.log
php_admin_flag[log_errors] = on

php_value[session.save_handler] = files
php_value[session.save_path] = /var/lib/php/session

If you are looking to view the processes, you will need to use different commands depending on how its been configured:

Example output of netstat -plnx:

unix 2 [ ACC ] STREAM LISTENING 146689 21372/php-fpm: mast /dev/shm/php-fpm-lukeslinux.co.uk.sock

Make sure that php-fpm hasnt hit max processes;

grep "pm.max_spare_servers" /etc/php-fpm.d/www.conf

ps -eo cmd,pid,pcpu --sort:-pcpu | grep -v grep | grep -c php-fpm