Vivekananda states the difference between sleeping and Samadi in the following lines from CHAPTER VII: DHYANA AND SAMADHI of Raja Yoga. In short, sleeping does not cause any change in knowledge but Samadi state changes knowledge.
How, for instance, do we know that a man in Samadhi has not gone below consciousness, has not degenerated instead of going higher? In both cases the works are unaccompanied with egoism. The answer is, by the effects, by the results of the work, we know that which is below, and that which is above. When a man goes into deep sleep, he enters a plane beneath consciousness. He works the body all the time, he breathes, he moves the body, perhaps, in his sleep, without any accompanying feeling of ego; he is unconscious, and when he returns from his sleep, he is the same man who went into it. The sum total of the knowledge which he had before he went into the sleep remains the same; it does not increase at all. No enlightenment comes. But when a man goes into Samadhi, if he goes into it a fool, he comes out a sage.
Time for sleeping depends on the sleeping habits of the person and on average one needs to sleep around at least 6 days in general. Any person can wake the sleeping person or the person may voluntarily wake up after their feeling of sleepiness went.
I have two doubts:
Who decides the time of staying in Samadi state? Is it in hands of the person in Samadi or is there any fixed time to stay in Samadi state?
Can another person wake up a person who is in Samadi state?