Dell R300 VMware Esxi 4 - Advice

[StuartLittle]

Hello avid VMware experts!

We are currently running a Dell R300 server with a single Dual Core Xeon 3GHz CPU, 8GB RAM and 2 x 300GB 15K RPM SAS HDD’s.

The R300 is running ESXi 4.0 (build 181792).

Can someone advise as a rough estimate how many VM guests this specification of server could handle in it’s current hardware state?

I know that is very difficult to estimate depending on what guests os’es, workload and other factors will be running but for arguments sake state that we would want to try and squeeze 6 x Windows 2K3 servers (average of 2GB RAM) plus maybe a couple of smaller XP/Vista PC’s.

All systems would only really have between 2-3 users on each system on at any point. Would this spec of server be able to handle that described scenario?

Also with ESXi 3.5 am I correct in saying that if you try and allocate VM guests with more memory than is physically available in the host it will not allow you … with ESXi 4.0 it seems you can add as many VM’s with as much memory as you want without it complaining?

If that is true how would this affect performance and how can I work around this (resource allocation?!)?

I realise these are very vague and speculative questions but I would appreciate any advice from the dedicated vmware followers!

Kind regards,

Stuart Little

[DSTAVERT]

Presumably there is a reason you can't add more resources to the hardware. There is probably no reason you can't do what you want to do but it depends on the workload. Your users will tell you if it isn't working and you will need to go to plan B.

[StuartLittle]

Hello DSTAVERT,

Thank you for the quick reply! Do you ever leave these forums? (Please don't! Also the R300 can only support a single quad core CPU which i don't know if it will make a huge difference.

The main reason for asking was to get a rough idea as to how acceptable that spec of machine is for a light workload.

Was I correct in saying that ESXi 4.0 will let you add more RAM to VM's than is physically installed in the host server?

Thanks again for all your help.

[DSTAVERT]

It is easier to over commit CPU than it is for RAM. RAM overcommitment may have some real costs. ESX(i) can use Transparent Page Sharing (TPS) to save RAM. TPS makes use of the fact that some blocks of RAM may be identical (multiple identical OS's running identical applications). ESX(i) uses TPS to eliminate the redundant blocks. That doesn't mean that you won't have swapping but since you will have identical OS's you should gain from the use of TPS.