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Memory errors in Guest machines after adding extra 4GB RAM to Host

Source: microsoft.public.virtualserver
Sent: 07/14/2009
From: "Steve Buckley" <mrnecros(remove-this)@hotmail.com>
Message:

(Note: I am concurrently pursuing the possibility that this issue may be a
result of some weird memory hardware mismatch)
I built a Hyper-V Host server (Server 2008 Enterprise SP2) using an Intel
Pentium E8400 CPU on an Intel P43 chipset motherboard with 4GB of DDR2
800MHz RAM.
It was running very well (perfectly in fact) but as I was progressing
through my studies for exam 70-640 I realised I would need more machines and
hense more RAM.
Long story short, I added another pair of DIMMS (same specification but
different brand) and ever since then I have started getting really weird
memory errors in Guest machines.
By weird I mean, spontaneous reboots, blue screeens, Win32 errors...the
whole gamut.
I can generally make virtual machines fall over just by installing an O/S on
them, if they live through that then applying SP2 will fail (plus a host of
other random events in between.)
If I take 4GB of RAM out of the machine (either pair of DIMMS) then it
stablizes again.

I understand this is entirely 64bit architecture so this *should* not matter
at all but are there any known issues with operating above 4GB?
Maybe there is a need to do some BIOS level memory-hole remap or suchlike?

I have run numerous and thorough memory diagnostics using the Windows memory
checking tool and can't find ANY faults.
I have swapped the RAM into different slots etc...I have spent a week
prodding and poking around, this sort of thing is very time consuming.
As a last ditch effort I'm probably going to buy another set of exactly
matching DIMMS to troubleshoot further.

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Related Messages

Re: Memory errors in Guest machines after adding extra 4GB RAM to

Sent: 07/14/2009
From: Rob Pettrey
Message:

I'd either buy 2 more of the exact same sticks or larger capacity sticks.

I'm running (2) Poweredge 2900's with w2k8 SP2 and Hyper-V, both with 24 Gb
(soon to be 40 Gb) RAM, both with (4) VM's running on top, and no memory
issues.

But I am running Dell RAM from Dell...

Some VM's are 2k8, some 2k3, and some (soon to be all) of the 2k8 VM's are
running more than 4 Gb RAM.
--
Rob Pettrey
Microsoft Small Business Specialist

"Robert Comer" wrote:

Show quoted text

> >I understand this is entirely 64bit architecture so this *should* not matter
> >at all but are there any known issues with operating above 4GB?
>
> No, there should be no issues with that. It's a server product and
> would be pretty useless if it only supported 4G of RAM.
>
> It sure sounds like you either have bad RAM, a bad RAM socket, or as
> you say, a timing issue.
>
> >Maybe there is a need to do some BIOS level memory-hole remap or suchlike?
>
> I've never had a PC that had that as an option in the BIOS and I
> really haven't had any similar problems with Hyper-V. I don't think
> it should be an issue in any case given how RAM is allocated.
>
> --
> Bob Comer
>
>
> On Tue, 14 Jul 2009 14:57:41 +1000, "Steve Buckley"
> <mrnecros(remove-this)@hotmail.com> wrote:
>
> >(Note: I am concurrently pursuing the possibility that this issue may be a
> >result of some weird memory hardware mismatch)
> >I built a Hyper-V Host server (Server 2008 Enterprise SP2) using an Intel
> >Pentium E8400 CPU on an Intel P43 chipset motherboard with 4GB of DDR2
> >800MHz RAM.
> >It was running very well (perfectly in fact) but as I was progressing
> >through my studies for exam 70-640 I realised I would need more machines and
> >hense more RAM.
> >Long story short, I added another pair of DIMMS (same specification but
> >different brand) and ever since then I have started getting really weird
> >memory errors in Guest machines.
> >By weird I mean, spontaneous reboots, blue screeens, Win32 errors...the
> >whole gamut.
> >I can generally make virtual machines fall over just by installing an O/S on
> >them, if they live through that then applying SP2 will fail (plus a host of
> >other random events in between.)
> >If I take 4GB of RAM out of the machine (either pair of DIMMS) then it
> >stablizes again.
> >
> >I understand this is entirely 64bit architecture so this *should* not matter
> >at all but are there any known issues with operating above 4GB?
> >Maybe there is a need to do some BIOS level memory-hole remap or suchlike?
> >
> >I have run numerous and thorough memory diagnostics using the Windows memory
> >checking tool and can't find ANY faults.
> >I have swapped the RAM into different slots etc...I have spent a week
> >prodding and poking around, this sort of thing is very time consuming.
> >As a last ditch effort I'm probably going to buy another set of exactly
> >matching DIMMS to troubleshoot further.
>

Re: Memory errors in Guest machines after adding extra 4GB RAM to Host

Sent: 07/14/2009
From: Robert Comer <(email address - cut out)>
Message:

>I understand this is entirely 64bit architecture so this *should* not matter

No, there should be no issues with that. It's a server product and
would be pretty useless if it only supported 4G of RAM.

It sure sounds like you either have bad RAM, a bad RAM socket, or as
you say, a timing issue.

I've never had a PC that had that as an option in the BIOS and I
really haven't had any similar problems with Hyper-V. I don't think
it should be an issue in any case given how RAM is allocated.

--
Bob Comer

On Tue, 14 Jul 2009 14:57:41 +1000, "Steve Buckley"
<mrnecros(remove-this)@hotmail.com> wrote:

Show quoted text

>at all but are there any known issues with operating above 4GB?
>Maybe there is a need to do some BIOS level memory-hole remap or suchlike?
>(Note: I am concurrently pursuing the possibility that this issue may be a
>result of some weird memory hardware mismatch)
>I built a Hyper-V Host server (Server 2008 Enterprise SP2) using an Intel
>Pentium E8400 CPU on an Intel P43 chipset motherboard with 4GB of DDR2
>800MHz RAM.
>It was running very well (perfectly in fact) but as I was progressing
>through my studies for exam 70-640 I realised I would need more machines and
>hense more RAM.
>Long story short, I added another pair of DIMMS (same specification but
>different brand) and ever since then I have started getting really weird
>memory errors in Guest machines.
>By weird I mean, spontaneous reboots, blue screeens, Win32 errors...the
>whole gamut.
>I can generally make virtual machines fall over just by installing an O/S on
>them, if they live through that then applying SP2 will fail (plus a host of
>other random events in between.)
>If I take 4GB of RAM out of the machine (either pair of DIMMS) then it
>stablizes again.
>
>I understand this is entirely 64bit architecture so this *should* not matter
>at all but are there any known issues with operating above 4GB?
>Maybe there is a need to do some BIOS level memory-hole remap or suchlike?
>
>I have run numerous and thorough memory diagnostics using the Windows memory
>checking tool and can't find ANY faults.
>I have swapped the RAM into different slots etc...I have spent a week
>prodding and poking around, this sort of thing is very time consuming.
>As a last ditch effort I'm probably going to buy another set of exactly
>matching DIMMS to troubleshoot further.

Resolved: Memory errors in Guest machines after adding extra 4GB RAM to Host

Sent: 07/17/2009
From: "Steve Buckley" <mrnecros(remove-this)@hotmail.com>
Message:

Thanks everyone for your advice and input.
I bought another pair of DIMMs from the same manufacturing batch as the
second pair ("Elixir" brand.)
Everything works fine now.

I think this is noteworthy for anyone building a Hyper-V system:
Make sure you have *exactly* matched memory.
There was absolutely nothing "wrong" with the RAM I swapped out.
It passed multiple "Extended" checks with the Microsoft Memory Checking Tool
(and is now happily humming along in my workstation...)
Also make sure that your processor supports virtualization (it will say so
on the box, if it doesn't...then it doesn't)

All things said and done, I can attest that it is possible to build a very
workable study/test Hyper-V server for about US$500.
My rig comfortably runs Server 2008 Enterprise as the host + 3 x Server 2008
Enterprise + 3 x Server 2008 Core Enterprise + 2 x Vista workstations
concurrently as guests.
Core Server requires very little RAM, you can install and run it with just
384MB.
Full Server works well with 768MB unless you are running Exchange, SQL or
suchlike (increase memory as you need it.)
Vista running Office 2007 needs 1GB+

1 x Asus Intel P43 Motherboard (P5QL-E)
1 x Intel E8400 Core Duo 3.0GHz CPU
4 x Elixir 2GB DDR2 800MHz Memory DIMMs
1 x 160GB SATA hard drive (for host system, ISO images, install files and
..vxd templates)
1 x 500GB SATA hard drive (for guest machines)

Having 2 hard drives is a must, even running 1 guest on the same drive as
the host system slows things down immeasurably.
If you have a bit more cash to spend then go for more hard drives to spread
your guests over.

One last note - most BIOSes have a feature to re-map the PCI address space
away from 4GB to 32GB to allow for 64bit O/Ses.
Do NOT disable this unless you want to make your server crawl like snail!

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