is Intel VT-d "really" necessary?

[SilverNodashi]

Hi all,

I'm just curios and would like some input from the community on this one. We're busy budgeting for a couple of new servers and I thought it would be good to try out the Core i7 CPU's, but see the majority of them don't offer VT-d, but just VT-x. Looking at the LGA1366 range, only the "Intel lga1366 i7 980XE" (from the list of what our suppliers stock) have VT-d, and it costs 4x more than "Intel lga1366 i7 930" or 2x more than "Intel lga1366 i7 960". From a budget perspecitve I could purchase 4 more CPU's, which could translate to 40x - 80x more VM's being hosted for the same capital outlay. Experience has shown that we under-utilize CPU's by a great margin and memory / HDD IO is our biggest bottleneck on any server.

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.

 

[Pada]

VT-d is not CPU specific but rather motherboard specific. See http://wiki.xensource.com/xenwiki/VTdHowTo
If you want to read more, see http://www.intel.com/technology/virtualization/technology.htm

I would reckon that VT-d is crucial if you want to run multiple Virtual Machines that will be doing lots of I/O.

The Intel i7 950 was sold for like R2200 ex VAT at Sahara a few weeks ago.

 

[kayvee]

The Intel i7 950 was sold for like R2200 ex VAT at Sahara a few weeks ago.

That's the new going rate for it since Intel announced the end August price drop, so it's about best value in the lineup.

 

[SilverNodashi]

VT-d is not CPU specific but rather motherboard specific. See http://wiki.xensource.com/xenwiki/VTdHowTo
If you want to read more, see http://www.intel.com/technology/virtualization/technology.htm

No quite. The CPU's need to support VT-d, not just the motherboard

 

[Pada]

No quite. The CPU's need to support VT-d, not just the motherboard

Where did you get that information?

Its very difficult to find information on the CPU's with VT-d support. I've seen that the i7 8xx (socket 1156) CPU's have VT-d support. eg. Intel® Core™ i7-860 Processor

However, I found this

Information
VT-d is not a feature of the processor itself but rather a feature of the Chipset. As long as the chipset/BIOS combination support VT-d and the processor support VT, there will be VT-d support.

at http://www.intel.com/support/processors/xeon5k/sb/CS-031637.htm

Here's a guide that will tell you if you should go for VT-d or not:
http://software.intel.com/en-us/blo...ect-device-attach-in-your-virtualized-system/

 

[SilverNodashi]

not all CPU's support VT-d, FYI

http://ark.intel.com/Compare.aspx?i...318,48139,47935,47934,47932,49158,48500,48499,


The following CPU's doesn't support VT-d:
http://ark.intel.com/Product.aspx?id=48499
http://ark.intel.com/Product.aspx?id=37149
http://ark.intel.com/Product.aspx?id=37148
http://ark.intel.com/Product.aspx?id=37147
http://ark.intel.com/Product.aspx?id=37150
http://ark.intel.com/Product.aspx?id=37153
http://ark.intel.com/Product.aspx?id=48499

The following supports VT-d:
http://ark.intel.com/Product.aspx?id=48500
http://ark.intel.com/Product.aspx?id=48498
http://ark.intel.com/Product.aspx?id=41315


I know VT-d is mainly used to better I/O pass-through and is generally used when you need a virtual machine to directly have access to a PCI / serial / USB peripheral.
What I don't know, is if anyone in the web hosting industry has had any worthwhile experience in actually using VT-d, i.e. can I gain from it? Our web hosting virtual machines don't need direct access to any PCI / serial / USB devices.

 

[Pada]

I'm 200% sure that the Core i7 9xx series CPU's also "supports" Intel VT-d! VT-d is a feature of the motherboard and not a feature of the CPU, unlike VT-x which is a feature of the CPU.
Those product sheets doesn't explicitly say "No" for Intel VT-d support. There are a lot of idiots out there who are posting on forums that VT-d has to be supported by the CPU too.

I've enabled VT-x and VT-d on my Asus P6T Deluxe v2 motherboard and I have an i7 940. Unfortunately I have no idea on how to use VT-d, since VirtualBox doesn't support it yet

There are other benefits of using VT-d, besides the obvious I/O performance increase. See http://software.intel.com/en-us/art...s-for-efficient-virtualization-of-io-devices/
Hopefully someone with experience in web hosting can help you out here. I only have experience with VirtualBox (on workstations) and very little experience with Microsoft HyperV (on servers).

 

[SilverNodashi]

Pada, are you just trolling, or did you actually read through all the links? There's a comparison chart as well which clearly indicated TV-d isn't support on all CPU's.

 

[Pada]

SofDux-Rudi:
I have read through all those links.

I'm now going to post on a few other forums about VT-d support on i7 9xx CPU's / VT-d not being CPU specific.
I'll give you feedback as soon as I've received replies confirming what I've said.

 

[Pada]

SoftDux-Rudi:
The people have confirmed what I've said all along: that VT-d is chipset specific, which means that the i7 9xx series CPU's "supports" VT-d if the motherboard supports it!
My threads:
http://forum.twilightgaming.co.za/index.php?/topic/4688-intel-vt-d-support/
http://www.tomshardware.com/forum/290293-28-support#t2173178

Seems to me like the people at webhostingtalk.com suggested that you should go for Xeon CPU's that supports ECC memory...
It's a real shame that no one else contributed to this thread