How much memory does unRAID require?
Prior to v4.3, unRAID required a minimum of 512MB, to a maximum of 1GB. It was recommended that 2 matched sticks of 512MB be installed, to take advantage of dual channel mode. As of v4.3, a maximum of 4GB is supported, and higher amounts will probably be supported in the future. See the forum threads mentioned in the next question as to why more memory can be helpful.