There was really no famine in Ireland, there was a property crisis. Ireland is extremely fertile, yet from about 1800 and onwards large parts of fertile land simply lay there, unused, no-one farming it. (It was due to this that the Irish got the reputation for being lazy) Had this land been farmed there would have been no famine in Ireland.
So why was so much wonderful land simply unfarmed? A few hundred years earlier the protestant feudal England had taken Ireland and made laws so that catholics could not own land. As a consequence huge areas of land were expropriated by the state and given to the protestant nobility. The catholic irish then became de facto serfs, simply RENTING the land that they had owned and worked for centuries. Then in 1797 there was a currency crisis and as a consequence the rent rose dramatically, so much so that it was not profitable for the farmers to rent the land. During the entire famine food was being EXPORTED from Ireland to England.
After the famine the Irish started land reforms to return the land to the original owners that had been robbed of their land by feudalists. This largely rectified the problem. Sadly, however, people today believe that this perfect example of feudalism somehow had anything to do with laissez-faire.