> 1) using VCB you take off the load from the ESX server (VCB proxy
sends the data to TSM, ESX just creates the snapshot)
>I am sorry, but I do not understand, how it is possible take off load
from ESX server. After creating snapshot you still need to read full
image or some files and send to proxy.  Almost the same is with normal
TSM backups excluding load, created by TSM Client. Maybe I am wrong, but
I really do not understand why?

Files are not SENT to the proxy.  Using a VCB function, the snapshot of
the .vmdk file is just MOUNTED to the proxy machine across the san.  The
proxy machine does all the work of the backup, it reads the snapshot
files and sends them to TSM server.

Go to www.redbooks.ibm.com, download SG24-7447, TSM 5.4-5.5 Technical
Guide. Read Chap. 24.
This is for TSM 5.5 client support ( 6.1 has more improvements), but it
explains how the proxy backup works with VCB very well.