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esxi ram  and cpu configuration

mun_84
mun_84 asked
on
HI experts,

I have a 14GB IBM server and i have allocated 10GB for sbs 2008 and 4 GB for server 2003 (32bit). Recently i was reading somewhere that we shouldn't allocated all the memory available and leave some for ESXI. Can you let me know what is the best allocation to configure my ram?

In terms of CPU? i have 2 quad cores and i give 4 x vcpu to sbs and 4 x vcpu to server 2003. How should i allocate this too.

I want my environment to run as fast as possible.

Regards,
HM
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Muhammad MullaSystems Administrator

Commented:
According to vmware:

http://pubs.vmware.com/vsp40_e/resmgmt/wwhelp/wwhimpl/common/html/wwhelp.htm#href=r_overhead_memory_on_virtual_machines.html&single=true

it looks like you should leave 5GB. Personally, I would take one away from server 2003 32 bit (as it cannot use the full 4 GB anyway) and two from SBS 2008.

8GB for SBS
3GB for Server 2003
3 GB for ESXi.

Author

Commented:
how about cpus? does it matter. By giving to ESXi memory does that mean just leaving it unallocated?
Top Expert 2010

Commented:
Oh my!....yes, do not use all RAM for VMs. The host will need about 2-4GBs for it's use. As far as CPUs go, just configure your VMs with the default amt (1...but for SBS, whatever the Sys Req is...2 vCPUs I would suppose...hadn't looked at the SBS Sys Req's). If you over-commit vCPUs to your VMs, you actually can degrade VM performance. I recommend reviewing the Resource Mgmt Guide for more detailed info:
http://www.vmware.com/pdf/vsphere4/r40_u1/vsp_40_u1_resource_mgmt.pdf

Regards,
~coolsport00
Markus VordererOwn Company

Commented:
The Overhead Memory on Virtual Machines Table OfflineGeek Points is the RAM which is needed by the severals CPU's

VMWare manages it's RAM in an own way.
I think that the Ram configration are to high for the VM's. You could get into performance leaks when VMWARe starts to swap the Ram. I would give the SBS 6 to 8 GB and the W2K3 2 to 3 GB.
Also the vCpu's are overcomitted.
Take a look inside your VM's. If there is any Software which can use all virtual cores you configured than the config will be fine.
but i think, that your SBS get better performnce with 2 vcpu and the W2k3 whith one vCpu.

Regards

Markus
Top Expert 2010

Commented:
Just keep in mind, as a general rule, that within your virtual infrastructure there is no difference than in the physical world. You allocate resources to your VMs like you would if they were physical boxes. Over-allocating can degregate performance. The min RAM for SBS is 4GB (see: http://www.microsoft.com/sbs/en/us/system-requirements.aspx), so if you would bump it up to 6GB, that should more than suffice. You can always monitor performance within the VM and your ESXi host and bump it up if needed. Unless your 2K3 VM is doing alot of work, there is no need to go higher than 2-3GB (2GB for starters).

~coolsport00
Hi,

Agree with CoolSport00, always provide only the default requirements of any OS.
And then while running the Operating System if you face any issue with Performance you can always increase the required memory.Also this would ensure that the remaining available memory can be allocated incase a newer requirement comes up.
This would also ensure performance tuning, over allocation of resources always causes an issue while troubleshooting performance related issues.
Also note that the memory requirements is usually to be provided in sync with the Server requirements and the Application installed recommendations in order for the application to work fine. Any provisions over and above the requirement would be idle resources and it is best that they be available with the ESXi Server rather than with the VMs.

Author

Commented:
So i've decided to go with these settings

8GB for SBS
3GB for Server 2003
3 GB for ESXi

2vcpu for SBS
1vcpu for Server 2003

Do i just power down the server and make this changes. Will these have ANY effect to my environment?
Top Expert 2010
Commented:
Yep...just power down your VMs to make those changes. Will what have any affect?...adding/modifying the CPU/RAM resources? Yes/no...it will affect performance on your VMs, more than likely increasing it. While your VMs are down, you will obviously have interruption of domain services for a brief time.

Regards,
~coolsport00

Author

Commented:
Perfect!! Do you have a VCP?
Top Expert 2010

Commented:
Yes :)