very poor svn checkout performance in win7pro(64bit)

I'm now using view(5.0.1.640055) , and linked-clone 64bit win7 with office,winrar ,etc.it works fine.

Problem is with TortoiseSVN. I use this SVN client with a SVN server(also installed in a virtualized win2008r2) for development.

When I checkout the code(about 8000 small files in about 1000 directory) from server, the files downloading is very slow, and even get a error:

Could not read chunk delimiter:Secure.

connection trunked.

But when I copy these files from TortoiseSVN redo-broswer, or export these files, it works OK.(slower than phsical win7)

I also test:

checkout 15 files/657MB, it OK.

export 15 files/657MB, it OK.

I guess checkout need more disk performance than other operations.

and in virtualized win7, checkout has exceed disk performance.

So, what's the reason? and how to solve it?

thanks a lot.