Rsync and DTrace

[diversos]

 Hello all..
 Using dtrace on solaris 10, i could investigate a performance issue with the sincronization of some files on a ZFS filesystem. I have started the follow rsync command (inside a gnome-terminal):
 
 /opt/sfw/bin/rsync -av -e ssh user at IP:/DirA/DirB .

 The current directory(.), was a ZFS pool with two SATA discs (mirror)... 
 The performance was terrible. After some tests with raid0, raid1, non-SATA discs, and using DTrace, i have realized that the problem was the "gnome-terminal". Basically the "-v" switch. 
 I'm preparing a document to post on my blog
 (www.posix.brte.com.br/blog), but i want your insights about:

 1- How the "-v" switch works? I mean, the rsync "waits" for the terminal is "ready" to display text (stays blocked)?
 2- The system was idle (98%), and the 1,5% was running gnome-terminal.. the iostat did show me 1M per 10 minutes (more or less). Could the driver (pipe) be the problem?

 I want the opinion of the developers to know if the "rsync" can be the "problem" (it was waiting). Or i can continue my investigation on kernel (driver) and gnome-terminal?

 How that conversation (pipe) works? 
 If i execute the same comand line on a console, or ssh session, everything works fine. If i execute almost the same command (without the "-v" option) and  put the process to backgound ("&"), everything works fine (not so fast, but a good performance).

 Thanks very much for your time.

 MSL