> So, if VT-d really necessary? > We mainly host XEN virtual machine for the hosting industry, i.e. we > don't need / use graphics rendering inside VM's, or need DAS on the > VM's, etc. > Kind Regards > Rudi Ahlers > SoftDux VT-d is not a necessity in general. It all depends on the kind of virtualization you run. If you run only paravirtualized guests on Xen, then there is not any need for VT-d (see [1]). If you fully virtualize for instance Windows guests, then specific systems may profit i.e. from a reserved network card by better network I/O. Whether VT-d is useful to have may too depend on whether pricing for the customer can be adjusted when providing such an extra feature. >From own experience I concur that often with most modern x86 architecture systems the I/O (network and storage) is the bottleneck in the area of virtualization. Just curious, do you really run virtualization for hosting on systems with uni-processor design? I mean not choosing professional dual quad- or hexa-core processor systems with Nehalem / Westmere Xeon CPUs or their AMD Opteron counterpart? Regards Alexander [1] http://wiki.xensource.com/xenwiki/VTdHowTo