SVN update takes too long - bug or not?

Win7 x64, SVN 1.6. My project has next directory structure:
/ <- svn root
|... folders
|---/products folder <- another svn root
|   |.... folders
    |----/tests <- another svn root with 3 svn externals
    |... folders and files
|... folders and files

Update process takes about 20 minutes. It is ok that Phpstorm sees all svn roots in subfolders and updates all. But it takes too long. Also I tried to configure manually vcs roots in phpstorm settings - it didn't help, still ~20 minutes to update.

Is it bug and I should file it to bugtracker or it is a normal behaviour?