Maximum memory for VM guest in ESX 3.0.1

[dborgill]

I have searched for this I keep coming up with mixed answers and a lot of old ESX 2.5.x articles.

We have Windows 2003 Enterprise hosts in ESX 3.0.1 - The host is an IBM x3950 with 16 gig of RAM. We have a request for a large SQL server that need 8 gig of RAM.

What is the OS and VM limitation for a 2k3 Enterprise guest?

[boydd · Accepted solution]

16GB RAM per VM - W2K3E will be able to handle 8GB RAM with no problems (I think the max is 32GB for W2K3E).

DB

[dborgill]

What about the non enterprise Server 2k3? Also, was this limit increased with ESX 3.0 vs ESX 2.5.x ?

[MR-T]

The limit went from 3.6GB in ESX 2.5 to 16GB in ESX 3.x

You can give a Windows 2003 standard server 16GB, but I don't think it can make use of it all.

[Dave_Mishchenko]

With Windows 2003 R2 standard x86 the OS is limited to 4 GB, but if you run x64 then you could go a high as 32 GB (althoughth you would be limited to 16 GB on ESX).

http://www.microsoft.com/technet/windowsserver/evaluate/system-requirements.mspx

[soleblazer]

I'm trying to comprehend why one would even need a 16gb memory vm

[dborgill]

Yeah, we have an Altiris-NS server that we are moving from a physical server with 8 gig of RAM to a VM.. just trying to figure out best performance/best practice.

[MR-T]

I guess the same people who require a 1000 port virtual switch

[Sticky]

You might find this helpful

Configuration Maximums for VMware Infrastructure 3

http://www.vmware.com/pdf/vi3_301_201_config_max.pdf

[grasshopper]

I guess the same people who require a 1000 port

virtual switch

ROFL

[DeeJay]

Playing devils advocate here, suppose you had a physical machine which runs mathematical computations and uses 32GB of memory. However, the tools that is used only runs on certain OS's.

Then further assume that the latest spec hardware from your chosen hardware vendor is not supported on that OS. Also assume that you'd like to be able to guarantee further hardware could be used with the system and ideally move the OS between physical hardware on the fly when you upgrade hardware.

How'd you do it? Surely no-one would use VMWare for that? Well, nobody apart from me it would seem! However, I'm stuck with the 16GB VM limit.

Unfortunately, this means that unless the 16GB limit is raised I'm stuck with Xen (and no VMOTION capability)...

Anyone know if 16GB is likely to stay fixed in 3.1.0?

Oh, and no, I don't need a 1017 port switch

Message was edited by:

DeeJay

[daat]

oh oh!

😮

i was hoping that i could use more than 16gigs of ram for a vm on my 32gig server

damnit!

any way to come round that limitation?

[jgswinkels]

Yes,

do not virtualize this system

cheers,

Jan

[daat]

wohoo!

theres a reason why i want to virtualize it... so... not acceptable

[JonT]

I think we would all love to hear why your VM needs more than 16GB.....

[DeeJay]

I thought I'd explained my reasoning? We run mathematical simulations on RedHat which consume to up 30GB of memory.

I'd love to be able to use ESX to run them, but I can't and am currently attempting to resist the introduction of Xen.

Why use virtualisation? Because the OS that the application is certified for does not run on the latest HP hardware, and we'd like to guarantee future compatibility. Hardware abstraction through virtualisation gives us that.

[grasshopper]

perhaps you can scale it out across multiple VMs?

[formulator]

If you need that much memory IMO either it's not a good idea to virtualize or it should be split across multiple VMs with smaller amounts of memory.

[daat]

hi jont

well, a fairly big db should run on it, and i would like to use as much mem as possible for it...

so, if i could assing 30gb of mem to the sql server there, it would be way better than 16gb

but, seems that doesnt work...

[DeeJay]

In my case, the job is already split across multiple machines and cannot easily be split further.

The long and short of it is that a) Virtualisation does give us benefits with this task and b) ESX does not support enough memory and Xen does.

I don't quite understand peoples comments about it not being suitable for virtualisation. Why not? If it's running on a machine equipped with 128GB of memory then I could feasibly run 3 or 4 similar VM's. That's not massively different from running 4 2GB VM's on an 8GB starter edition ESX box is it? The key issue here is that we must use an older version of Linux and virtualisation guarantees a stable (ish) hardware platform which the OS supports. I cannot guarantee that with changing hardware specs from vendors.

So, to put it another way, what other technology could I use to move machines between physical hardware on the fly (the jobs take days to complete and this is a useful feature if hardware starts to fail) and that can guarantee I'm able to run old versions of Redhat on HP's latest and greatest hardware?

I presume no-one has heard of any plans to increase the limit further on ESX? With the support of 64 bit OS's, I guess the amount of memory needed in VM's is only ever likely to increase and at the moment VMWare is worse than Xen in this respect, which can't be a good thing.