Caution: Articles written for technical not grammatical accuracy, If poor grammar offends you proceed with caution ;-)
OK, so my last post brought on a blizzard of remarks questioning some of the validity of the data presented. I used what I was told during a presentation was a “Gartner recommended” configuration for a VM. My error was that I could not find this recommendation anywhere, but the sizing seems fairly valid, so I went with it. I went back to some of the assessments I have done and took data from about 2,000 servers to come up with some more real-world averages. I wanted to post these averages tonight. Remember what I said previously: This is just a set of numbers. You must ASSESS and DESIGN your virtual infrastructure properly. This is only a small piece of it.
I apologize for the images instead of tables, but I spent way too long trying to get tables to lay out properly in WordPress. Click on the images for larger views. I can post the raw data if someone wants to look at it, but I have to work on stripping away proprietary data first. So, here we go:
If you have ever done a Virtualization Assessment, you will recognize this from the summary page of the workbook. We are going to look at data from 1956 servers. Average RAM usage is about 2069MB. Average CPU utilization is about 5.2%. Average network is about 31KB/s.
From the same page in the workbook. From this chart, we see that the average ALLOCATED RAM is about 4342MB and the average FREE RAM is about 2273MB. This is where we get the average RAM usage from above.
This is the averages calculated for each row in the raw data summary.
This final chart is from a storage summary report. Average disk read bytes per sec (442,00) + average write bytes per sec (200,000) is about 600,000 bytes. So, total I/O bytes is about 632,000 (600,000 storage + 32,000 network). I used Google to convert this to gigabits: 632 000 bytes = 0.00470876694 gigabits. This is WAY less than the 0.3Gb recommended. So, here is my calculated AVERAGE VM sizing:
- RAM = 2GB
- I/O = 0.005Gb
- Network I/O = 0.0002 Gb
- Storage I/O = 0.004 Gb
I am not going to claim that this is my recommendation for a VM configuration, because it isn’t. My recommendation is still and will always be to ASSESS YOUR UNIQUE ENVIRONMENT and come up with your own data. I am not going to redo my previous post with these numbers because it is pointless. The intent of the previous post was to come up with a number of VMs in a chassis or rack based on a set of criteria. I also wanted to show a comparison of capabilities of each blade. If I use the numbers from this post, it will only show that each blade in question is capable of hosting even more VMs.
This is consistent with some assessments I’ve done. Looks like big enterprises like a lot almost unused servers. On a recent project I finished, I can see 90% of VMs using very few resources, and 10% of VMs really using resources more heavily (BD servers mainly I would say).
These numbers you assesed, especially the IO numbers are much more real-world relevant. I have no idea how Gartner/the presenter came up with those 0.3 gbit/s as TYPICAL IO requirements for a VM. Sure there are cases with high loaded databases servers and stuff, but these are rare exceptions.