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I want to setup a number of guests with multiple CPUs (4) and at least 4Gb ram running Ubuntu Linux. These machines will mostly be idle, but from time to time their workload will require all their resources, especially the CPU.

The hosts are ESXi 5.x.

The question is, am I right in thinking that the resource consumption of the machines when idle will be negligible?

We know this true of disk and the CPU. The only concern left therefore is memory. Since ESX over-commits memory it makes sense that unused memory of any guest is paged out.

If my thinking correct?

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up vote 0 down vote accepted

Yes, idle memory is swapped, or ballooned.

If you have simmilar machines (same OS, etc), the memory is also nicely deduplicated (same data from different machines (eg. most of the the operating system) is stored only once in memory).

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Just enable the vmmemctl (balloon) driver in your guests. It should be included as part of your VMware Tools installation. This lets VMware reclaim memory that a guest isn't using.

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Thank you! I marked mulaz answer as correct for the added deduplication information is pertinent as well. – cmdematos Oct 25 '12 at 19:07

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