1. Is the P2V conversion is possible for the Unix or Linux Machines in ESX.
Yes, for some Linux distros.
See: http://www.vmware.com/support/pubs/converter_pubs.html
For others you can do (with the Converter Enterprise CD) a cold image, but you have to manually fix the storage and network drivers.
2. If we convert from Physical machine to Virtual machine do we can change the disk space as provided in the Physical machine.
Yes, with Converter Standalone 4.x and supported Linux distros.
Andre
Andrew | http://about.me/amauro | http://vinfrastructure.it/ | @Andrea_Mauro