dgowan777
Contributor
Contributor

ESX 5.1 detected one half of my RAM

Dear Community,

I just built a new system to host multiple vm's:  AMD FX 8320 (8 core), 32GB RAM with 2 1TB disks.  The BIOS sees all 32GB of RAM.  After installing ESX 5.1, it's reporting only 16GB of RAM.  I added my license, but still only 16GB of RAM. 

What do I need to do for ESX to recognize all of my memory?

Thank you.

Darin

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13 Replies
aravinds3107
Virtuoso
Virtuoso

Welcome to the Communities..

It looks like some hardware configuration and nothing related to ESXi. Even the free ESXi would support upto 32 GB memory.

Check fo any advance option for Memory in the BIOS. Check the discussion and see if it helps http://communities.vmware.com/message/2164387

If you find this or any other answer useful please consider awarding points by marking the answer correct or helpful |Blog: http://aravindsivaraman.com/ | Twitter : ss_aravind
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Rumple
Virtuoso
Virtuoso

you probably populated all the memory slots (or split your ram across all the memory slots, but only have a single socket on the motherboard filled.

You can't use both memory banks and a single Socket..each memory bank is tied to a socket...

the bios will see it, but because of NUMA, its not usable...

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ramkrishna1
Enthusiast
Enthusiast

Hi

Welcome to the communities.

Its on guest machine or esx web portal ?

If esx web portal then definitely something configured wrongly

If its on guest machine you need to check respective OS & limitation.

"a journey of a thousand miles starts  with a single step."
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AKU076
Enthusiast
Enthusiast

Looks like a hardware issue you can check the following:

1. Is memeory mirroring enabled in BIOS ?

2. Check care fully on the system POST messages,  I have seen systems disabling memory modules after failing ECC checks. it detects the 32 GB but disables memory modules in case the ECC checl fails. Look carefully for error messages after rebooting the server before the ESX starts booting.

3. Finally another way is to find the total memory modules detected by the ESXi. for that you can follow the KB article

Once you have the cim diagnostic out put search for PhysicalMemory, Each module of memory detected by ESX host with serial number and the slot installed anc capacity will be displayed. By this i hope you can get some information on why it is not showing 32 GB on your server !!

memory_info.png

Hope This helps

Regards

AKU076

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dgowan777
Contributor
Contributor

Hi AKU076,

Thanks for your reply.

1. I don't see any options in my BIOS for memory mirroring.

2. I didn't see any errors during the POST (although it went by rather quickly)

3. The cim-diagnostic script shows that ESXi does "see" all four of my 8GB dimms, which is interesting.  Almost leads one to believe that mirroring is enabled.

Another related question, how does dual channel effect ESX's ability to "use" all of my RAM?

Not sure where to go next...

Thx.

Darin

Message was edited by: dgowan777 - attached the memory specific output from cim-diagnostic.sh

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dgowan777
Contributor
Contributor

Hi aravinds3107,

The thread you posted was interesting.  I see that my problem is kind of common.  I'm still searching...  I've also opened a request with my motherboard manufacturer, as I've tried running two other Linux (centos and fedora), both of which only see 16GB.

Thx.

Darin

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dgowan777
Contributor
Contributor

Hi Rumple,

When you say "each memory bank is tied to a socket", are you referring to the physical processor?  My motherboard only has one processor socket with four dimm slots.  However, the board does support "dual channel", which is activated when you have all four memory banks filled up (which is my case: 4*8GB DDR3).

Thx.

Darin

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AKU076
Enthusiast
Enthusiast

Hi,

this is interesting.. As few more steps, can you run esxtop with "M" options and paste the screen shots, Also if possible share the vmkernel, dmesg log files. (vm-support) logs will be better.

Ideally if the ESX sees all 32 G , i dont see any reasons for suspecting memory mirroring at BIOS level.

Anoop

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dgowan777
Contributor
Contributor

Hi all.

Thank you everyone for your comments and suggestions.  As it turns out, my processor was the problem.  I just replaced it with a new one and WHAM, all 32GB showed up.  Yes!

Thanks again.

Darin

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Gnome007
Contributor
Contributor

Thanks dgowan777,

your post of the CPU told me to check for the latest bios of the motherboard.

A bios update did the thing. Now the esxi 5.1 shows the full ram, not only half of it. No new CPU or other ram!!!

Thanks Smiley Happy

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Moralenco
Contributor
Contributor

Hello,

I have the same problem with the version 6.7

I have updated the chipset and the result its the same.

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daphnissov
Immortal
Immortal

Nothing that you have is supported to begin with. That said, check your motherboard documentation for the DIMM rank population order. It may be banks 1 and 3 first, not 3 and 4.

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Moralenco
Contributor
Contributor

Sorry, you’re right. I‘ve tried changing order and its working.

sorry for my mistake with the post

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