64-bit Guest OS on 64-bit Host

[GergMN]

Sorry, I know this subject keeps getting brought back up, but I've been unable to find an answer that helps me. I need a little insight.

I have a Dell PowerEdge 2850 with dual quad-core Intel Xeon processors (2.8Ghz) and 8GB of RAM. I can install and run ESXi 4.0 with no problems. I can also install Windows Server 2008 (x64 edition) on that server instead, with no problem. (I tried that first, actually, then decided to instal ESXi instead, and run Server 2008 as a VM.)

When I try to create a new VM on the ESXi host using the Server 2008 DVD, I get an error that the install failed because the CPU is not compatible with 64-bit mode.

I've downloaded & run the VT.ISO, and it does show that the cores do not support VT.

What I don't understand is how I can install ESXi or Server 2008, and run either one, both of which require a 64-bit processor, but I can't install a 64-bit Guest OS on the same server. What am I missing?

[HughBorg707]

How many CPUs are you gving the guest VM? I've seen some posts before that mention lowering the count to say, 2 or 4. Also refer here to compatability http://ntpro.nl/blog/archives/1061-CPU-compatibility-with-VMware-Fault-Tolerance.html

Even if just to isolate the problem I would try installing with 1, 2, or 4 CPUs in VM properties.

[GergMN]

I created this as a new VM, so went with the standard setup in the wizrad. It has 1 CPU and 4GB of RAM. When I start the install from the DVD, it stops almost immediately saying it couldn't be installed.

This is just an install of ESXi 4.0, and will be part of the Essentials Edition, so no FT or HA or anything fancy like that, just a bare-bones ESXi host running 5-8 VM's. If I could get a 564-bit Guest OS to install!

[Dave_Mishchenko]

Have you enabled Intel VT in the BIOS and done a cold restart?

[admin]

What I don't understand is how I can install ESXi or Server 2008, and run either one, both of which require a 64-bit processor, but I can't install a 64-bit Guest OS on the same server. What am I missing?

Running a 64-bit guest requires more than a 64-bit processor. Running any guest OS requires some mechanism for isolating the guest OS from the hypervisor. Using binary translation, the guest OS and the hypervisor share the same virtual address space. The hypervisor lives in the highest part of the address space, and the x86 segmentation mechanisms are used to prevent the guest OS from clobbering the hypervisor. Unfortunately, segment limit checks were removed from 64-bit operation in the original AMD64 specification. Though AMD has amended the AMD64 specification to include 64-bit segment limit checks, Intel has not done the same with EM64T. Thus, on an Intel CPU, some other mechanism is required to isolate the guest OS from the hypervisor. VT-x is such a mechanism. With VT-x, the hypervisor and the guest OS live in separate address spaces, so the guest OS cannot clobber the hypervisor.

[GergMN]

When I ran the VT.ISO, and it reported that the cores were not compatible with VT, does that mean I'm outta luck? Is that the key piece of the puzzle, or is there some other way around it?

I looked through the BIOS and couldn't find anything that would allow me to enable/disable any settings like VT, and I believe it's the latest version of the BIOS (A07).

[Dave_Mishchenko]

No that CPU doesn't have VT-x - http://ark.intel.com/Product.aspx?id=27097.

[admin]

You are probably outta luck. There is an Intel erratum (AW67) which can cause VT-capable CPUs to report that they are not VT-capable. However, if you have the latest BIOS, it is unlikely that you are running afoul of that erratum. If you post the vmware.log file for the 64-bit VM you tried to install, I can tell you whether or not AW67 is involved. Or, you can look up your processor capabilities here.

[DSTAVERT]

You are out of luck. I ran into the same problem on a server. I ran the iso and it told me it wouldn't work. I insisted it should. :smileydevil: ESXi 4 installs just fine and runs for a while but the hardware fails at some point. Ususlly in a day or two. The server cries out told ya!

[GergMN]

Shoot.

The HCL lists a PowerEdge 2850 as compatible, but it list the CPUID as "F27." Mine are "F48." For the life of me I can't find out which processor would be an "F27." There are tons of 2850's for sale, but I'll never be able to figure out which one is the right model. I did find one with dual 3.60 processors, but they're listed as not being VT-x compatible either.