Refer to page 30 of http://www.vmware.com/pdf/vsphere4/r40/vsp_40_resource_mgmt.pdf or page 136 of http://www.vmware.com/pdf/vi3_35/esx_3/r35/vi3_35_25_resource_mgmt.pdf
Memory overhead usage chart
Some examples:
With 1 vcpu and 256MB of RAM; the VM kernel requires 87MB for 32 bit VM’s and 108MB for 64 bit VM’s.
With 8GM of RAM and 1 vCPU you’ll need 188MB and 209MB for 32 and 64 bit.
With 4 vCPU’s and 8GB of RAM you’re looking at ~360MB for a 32 bit VM and 431MB for a 64 bit VM.
Note: memory overhead for 32-bit VMs generally increased between 3.0.1 and 3.5 while 64-bit overhead generally decreased.
ESX 3.5 Overhead
| ESX 3.5 Update 2 |
|||||
| Virtual CPUs | Virtual Memory (MB) | Overhead for 32-bit VM (MB) |
% Overhead for 32-bit VM | Overhead for 64-bit VM (MB) |
% Overhead for 64-bit VM |
| 1 | 256 | 87.56 | 34.20% | 107.54 | 42.01% |
| 1 | 512 | 90.82 | 17.74% | 110.81 | 21.64% |
| 1 | 1,024 | 97.35 | 9.51% | 117.35 | 11.46% |
| 1 | 2,048 | 110.40 | 5.39% | 130.42 | 6.37% |
| 1 | 4,096 | 136.50 | 3.33% | 156.57 | 3.82% |
| 1 | 8,192 | 188.69 | 2.30% | 208.85 | 2.55% |
| 1 | 16,384 | 293.07 | 1.79% | 313.42 | 1.91% |
| 1 | 32,768 | 501.84 | 1.53% | 522.56 | 1.59% |
| 1 | 65,536 | 919.37 | 1.40% | 940.84 | 1.44% |
| 2 | 256 | 108.73 | 42.47% | 146.41 | 57.19% |
| 2 | 512 | 114.49 | 22.36% | 152.20 | 29.73% |
| 2 | 1,024 | 126.04 | 12.31% | 163.79 | 16.00% |
| 2 | 2,048 | 149.11 | 7.28% | 186.96 | 9.13% |
| 2 | 4,096 | 195.27 | 4.77% | 233.30 | 5.70% |
| 2 | 8,192 | 287.57 | 3.51% | 325.98 | 3.98% |
| 2 | 16,384 | 472.18 | 2.88% | 511.34 | 3.12% |
| 2 | 32,768 | 841.40 | 2.57% | 882.06 | 2.69% |
| 2 | 65,536 | 1579.84 | 2.41% | 1623.50 | 2.48% |
| 4 | 256 | 146.75 | 57.32% | 219.82 | 85.87% |
| 4 | 512 | 153.52 | 29.98% | 226.64 | 44.27% |
| 4 | 1,024 | 167.09 | 16.32% | 240.30 | 23.47% |
| 4 | 2,048 | 194.20 | 9.48% | 267.61 | 13.07% |
| 4 | 4,096 | 248.45 | 6.07% | 322.22 | 7.87% |
| 4 | 8,192 | 356.91 | 4.36% | 431.44 | 5.27% |
| 4 | 16,384 | 573.85 | 3.50% | 649.88 | 3.97% |
| 4 | 32,768 | 1007.73 | 3.08% | 1086.75 | 3.32% |
| 4 | 65,536 | 1875.48 | 2.86% | 1960.52 | 2.99% |
| Averages | 408.30 | 11.51% | 453.30 | 15.29% | |
ESX 3.0 Overhead
| vcpu | vRAM | 32 bit overhead | 64 bit overhead |
| 1 | 256 | 79 | 174 |
| 1 | 512 | 79 | 176 |
| 1 | 1024 | 84 | 180 |
| 1 | 2048 | 91 | 188 |
| 1 | 4096 | 107 | 204 |
| 1 | 8192 | 139 | 236 |
| 1 | 16384 | 203 | 300 |
| 2 | 256 | 97 | 288 |
| 2 | 512 | 101 | 292 |
| 2 | 1024 | 101 | 300 |
| 2 | 2048 | 125 | 316 |
| 2 | 4096 | 157 | 349 |
| 2 | 8192 | 221 | 413 |
| 2 | 16384 | 349 | 541 |
| 4 | 256 | 129 | 511 |
| 4 | 512 | 133 | 515 |
| 4 | 1024 | 141 | 523 |
| 4 | 2048 | 157 | 540 |
| 4 | 4096 | 189 | 572 |
| 4 | 8192 | 222 | 605 |
| 4 | 16384 | 350 | 734 |