high i/o

I have a vmserver that houses 4 virtual servers.
sles 11 sp2 (groupwise, gwia, and gwaccess) gw 8 hp2
sles 11 sp1 datasync 1.24 966

datasync has gotten very slow %wa is 85 or higher compare to groupwise's less than 3
there are 120 users
why would io be so much more that the gw box itself?

what can i do to trouble shoot / fix the problem?
has anyone else seen this problem?
seems to have gotten worse since i upgraded to 966

thanks
tom