netbloke
Enthusiast
Enthusiast

Estimating host hardware requirement for xyz guest(s)

My VM machine is grinding to a standstill as I start more guests. Each guest runs fine when it is the only guest running. The host is an old machine we had lying about the office, I am not claiming it is a suitable platform (2.8GHz, 512MB, 40GB).

We are looking to replace the hardware with something more suitable. So, how do I estimate host requirements for a replacement. The guests are created with 256MB ram, 8GB hdd and OS is WinXP. I am aware of one application (runs on only a single guest) that tends to take 100% CPU if it can. Generally the guests are not very busy. OS of host and guests likely to remain some flavour of Windows.

How much RAM would be recommended for the host? What other requirements should I be aware of? Any useful links would be much appreciated. I have looked for guidance on the VM site. I found the Capacity Planner and VM Infrastructure, both of which appear to be massive overkill for this question. Are there any published guidelines or rules of thumb that I can use? I have found reference to each CPU core running 4-8 guests, but clearly this is not always the case.

Thanks in advance,

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2 Replies
birdie
Expert
Expert

RAM is dirt cheap nowadays so buy as much as you can. The bare minimum should be 4GB even if you have a 32bit host OS (BTW 32bit Linux kernel can see and work with 64GB RAM if your CPU supports 64bit extensions).

Your CPU should have as many cores as possibles - since it will greatly increase host OS responsiveness if your guests are using a lot of CPU cycles.

An ideal case will be: one CPU core for every guest, and memory amount can be calculated as a doubled sum of all guests RAM plus at least 1GB RAM for your host OS (in case of three guest with 256/512/768MB you should have (256512768)*2 + 1024MB of RAM for your host).

netbloke
Enthusiast
Enthusiast

Thankyou that's the sort of rule of thumb guide I was looking for.

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