Host and Virtual Machine RAM Allocation

[anthonyhelmey]

The ESXi host I have is installed with 32GB of ram. I have 5 VMs installed. How much RAM can I allocate to each VM? Right now there is 6GB on each host.

[a_p_]

This actually depends on the guest's real requirements, whether you use the same guest operating systems etc.. ESXi has a bunch of features built in to manage memory, e.g. transparent page sharing, memory compression, ballooning, ... (see http://www.vmware.com/files/pdf/mem_mgmt_perf_vsphere5.pdf)

Ballooning even reclaims currently unused memory from guest operating systems in order to provide it for other guests. This is one of the reasons why you should always install VMware Tools in the guest OSs.

André

[anthonyhelmey]

The guests requirements are for graphics rendering. The guests OS are running a custom Windows 7 Embedded, with Adobe After Effects pm each OS. Originally the host was the render engine, and it was running the 32GB of RAM, a Samsung 840 Pro SSD connected to a SATA 6G. Now there are 5 VMs sharing the hosts resources, and the SSD had to be moved down from a 6G SATA to 3G. ESXi would not load the HD while it was on the 6G. But the graphics rendering software needs loads of RAM and we are planning on having all 5 VMs booted and running After Effects at the same time.  VMWare tools are installed on all guest OS's.

[a_p_]

If the VMs are actively using the provisioned memory, there might not be much the host can do, and you should calculate 1:1 with the existing physical memory. I'd say 2GB for the host itself should be taken into account and the VMs will also require some Overhead Memory on Virtual Machines.

IMO you should be able to run the 5 VMs with 6GB each on this host. On the other side you may consider to add more memory to the host if possible.

André

[anthonyhelmey]

That was something I was thinking about. The rendering seems to be a bit sluggish, I have to wait for the expert to fly in from the UK. Then if he deems it necessary, we can up the RAM. Thanks for the help André