Segmented Sleep and R' Simcha Zissel Ziv, the Alter of Kelm

We've discussed polyphasic sleep and the Vilna Gaon earlier. Another type of sleep pattern that was much more common was segmented sleep, where one sleeps a bit during the day, and is up longer at night. (It's a bit more complicated than that, see the Wikipedia article linked above for more details.) The Alter of Kelm, R' Simcha Zissel Ziv, would - according to his student R' Yeruchum Levovitz - sleep three hours each night and half an hour during the day. But he was still able to learn Torah for eight hours straight.
R' Levovitz attributes R' Ziv's accomplishments to his sense of order and his fanaticism for methodicalness in life. R' Ziv would equate orderliness with the clasp of a necklace: "The jewels of the necklace are its most important component, while the clasp is the least significant. Yet if the clasp fails – all the jewels fall. Orderliness is like that – it not particularly important, but it protects everything that is important. If one is orderly and methodic then his Torah, his prayers, his mitzvos will remain protected – he can be sure that they will continue! But one who is disorderly – his jewels fall to the ground… One needs to awaken at a set time, to pray at set time, to begin his learning at a set time, and to stop learning at a set time!"