Sql-server – What RAID level do you use on SharePoint databases

It depends on what you're planning to achieve.

If you're going to have a small farm with small quantity of users, then this is something you don't have to take in consideration. However, when you're deploying a really large farm you should pay attetion to software boundaries.

As you can see in this Technet Article Plan for Software Boundaries, SharePoint degrades performance exponentially when certain things are not taken into account.

I would suggest you pay attetion to these performance issues, rather than site collections. Site Collections have their pro's and con's, however when you're working with large farms (100GB+), Microsoft suggests to use a single site collection and quotas for content databases. Hope this helps.

-Máximo

You don't mention whether this is a single server SharePoint installation or whether the SQL Server lives on another machine.

The reason why this is important is because you can save a lot of time by simply building up a new server, installing SharePoint to the same patch level as your original server, and connecting the new one to your existing server farm. Then run SharePoint Configuration Wizard on the old server to disconnect it from the existing SharePoint config, and finally amend your DNS entries.

If you are able to do this it will save a lot of pain!