> In the svn repository, the repository directory layout now is awful, I plan
> to reorganize the layout, But I don't know what's risk I will take.
> Q1:If I move sub1 from / to sub2 directory, will the log and revision still
> remain under sub1?
The history will be preserved and can be examined as usual using "svn log" and "svn blame". Any change to the repository, including moving directories around, will result in the revision of the repository being incremented.
> Q2:If I move sub1 from / to sub2 directory, the workcopy need to relocate or
> checkout initally?
Users who had the directory checked out from its old location and want to use their working copies with the same directory in its new location will need to go into their old working copies and run "svn switch newurl". Note that you will be using "svn switch", not "svn switch --relocate"; the former is for when the path of something inside a repository changes, while the latter is for when the URL of a repository itself changes.
You can of course test both of these scenarios and any others by creating a test repository and playing with it.