Thank you Adam.
Below are the answers I got from a NetApp Technical Support Engineer for the same questions:
1) It is not recommended having a volume with 10 LUNs reason being is if one LUN went off line it would take the whole volume off line. So having 10 LUNs in 10 different volumes is the best practice.
2) If you had 10 LUNs in a volume, you could not restore an individual LUN from the snapshot because it sees at block level and not file level.
I am a bit confused now..Do you know if NetApp has realased a whitepaper or some formal guidelines or best parcise guide about this?
1) Works only if do not have a large amount of LUNs. Otherwise you can run into number of volumes limits. And 1 LUN taking down the rest will only happen when your volume runs out of space.
2) Yes you can. Either use snap restore for a file (the LUN in this case) or LUN clone/split.