CPU VT-d I/O vs number of cores, what is more important?

[AntiMatter]

Hi,

I hesitate between two CPUs which are 64 bits and have VTx:

- Intel i5 6x, 2 cores which has VT-d, which I believe is to help virtualized I/O

- AMD Thuban 6 cores, and probably nothing equivalent to Intel's VT-d

Q1. For a better performace in virtualization (and not specifically with Virtualbox) what is more important between the two feature above? (More cores vs VT-d)

Q2. How to check if a CPU is compatible with Nested Paging? If you have experience with Virtualbox using Nested Paging, have you noticed any improvement?

Thanks in advance for any help.

[Perryg]

I feel your pain.

I don't believe that VBox uses VT-d (yet) but from what I have read it might be the next step in virtualization. But it is new and you know how that goes.
I have tested Intel vs. AMD and from what I see Intel is faster but more expensive. This is of course MHO!
Intel uses EPT or Extended Page Tables and AMD uses nested paging. I have seen some improvement using this but for my part I would not call it a show stopper if you don't have it.
SATA has to be the biggest improvement and virtio of course comes in a close second for my 2 cents.

[AntiMatter]

SATA has to be the biggest improvement and virtio of course comes in a close second for my 2 cents.

I guess you meant SATA on the host machine. So then it seems like in the short term future, until "Virtualization Technology for Directed I/O" (VT-d) becomes mature, 6 cores seems to be a better bet.

[Perryg]

Actually using SATA controller on the gust machine is what I was getting at. The throughput and speed is greatly improved using SATA instead of IDE in VBox.

[sej7278]

vt-d is not used by anything except some bleeding edge xen/kvm code as i recall, certainly not virtualbox/vmware, its only for direct pci access anyway, doubt if it would ever speed up disk/net, just might enable tv cards and such.

vt-x and nested paging are the most important, my core i5 has 4 cores, or are you talking about a laptop model?

wouldn't go with amd for anything these days, i wouldn't go for a core-i7 either as its too much more expensive than an i5 and will be superceded by i9 soon enough.

[AntiMatter]

vt-x and nested paging are the most important, my core i5 has 4 cores, or are you talking about a laptop model?

wouldn't go with amd for anything these days, i wouldn't go for a core-i7 either as its too much more expensive than an i5 and will be superceded by i9 soon enough.

I am talking about desktop CPUs. How do you check the CPU specs if it is compatible with nested paging?
For example: Intel i5-750 http://ark.intel.com/Product.aspx?id=42 ... odes=SLBLC

Any particular reason to avoid AMD? 6 cores + low wattage seems pretty interesting.

[sej7278]

vt-x and nested paging are the most important, my core i5 has 4 cores, or are you talking about a laptop model?

wouldn't go with amd for anything these days, i wouldn't go for a core-i7 either as its too much more expensive than an i5 and will be superceded by i9 soon enough.

I am talking about desktop CPUs. How do you check the CPU specs if it is compatible with nested paging?
For example: Intel i5-750 http://ark.intel.com/Product.aspx?id=42 ... odes=SLBLC

Any particular reason to avoid AMD? 6 cores + low wattage seems pretty interesting.

mine is an i5 750 and its quad core, 64-bit, with nested paging, pae/nx and vt-x, but no vt-d or hyperthreading. its very difficult to track down the specs from intel (especially concerning vt-d, which i eventually found is on no i5's and only some i7's).

to tell you the truth though, i don't notice any difference from my core2quad q6600 (no nested paging and clock speed is 3.2ghz not 2.66 like the i5) for day-to-day virtualisation use, i thought nested paging would make a lot of difference.

the main bottlekneck these days seems to be disk throughput - compiling stuff is pretty slow on virtualbox (growable not fixed vdi on a fast sata2 drive).

[redsparrow]

I believe the Phenom X6 does have an equivalent to Intel's VT-d called IOMMU/AMD-Vi. (http://en.wikipedia.org/wiki/VT-d#IOMMU)

To take advantage of the IOMMU on the Phenom, you need to use an 890FX (or maybe 890GX) chipset on your motherboard.

As someone pointed out, many of the Core i5's don't have VT-d. Some of the new dual-core (Clarkdale) i5's do have VT-d, but the rest of the i5's don't. http://en.wikipedia.org/wiki/List_of_In ... processors

Here is the VirtualBox ticket for VT-d/IOMMU support: http://www.virtualbox.org/ticket/5252

[liangsuilong]

VT-d and AMD-Vi are used for I/O Virtualization. Unlike VT-x and AMD-V, they are not widely used now. If many users need it, I think VirtualBox will add this feature.

Parallels Workstation Extreme 4 supports GPU direct rendering on VIrtual Machine via VT-d. But I doubt that It only works on HP Z800 series workstation. Is this the result that Intel combines HP and Parallels? I can not find out any productions in the market like that.

IOMMU is one of I/O virtualization technologies. Another one is SR-IOV. SR-IOV has better performance that IOMMU in theory. However, they are likely to use for different devices. Does anyone make a comparison between them.

[lom]

I believe the Phenom X6 does have an equivalent to Intel's VT-d called IOMMU/AMD-Vi. (http://en.wikipedia.org/wiki/VT-d#IOMMU)

To take advantage of the IOMMU on the Phenom, you need to use an 890FX (or maybe 890GX) chipset on your motherboard.

Hi,
actually only the chipset is important. The CPU itself doesn't have the IOMMU included.

Here is a list of Intel and AMD hardware wich support this: http://wiki.xensource.com/xenwiki/VTdHowTo

[sblantipodi]

Intel Sandy Bridge now support VT-D but I don't know if VirtualBox support it.