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At our company we set up an OpenStack Cloud and are currently creating internal guidelines for creation of OS templates / images. One controversial topic was if we should provide swap inside the VM templates. Therefore I'd like to ask the following questions

  • From an elastic Cloud provider point of view, does it make sense to offer swap partitions / files in the VM templates or is swap not needed when a VM can be resized?
  • Which scenarios necessarily demand a swap file to be present?
  • What kind of Storage should be used for swap files (e.g. local / central, FC / iSCSI / NFS)?
  • Are there any best practices for offering swap files in a performant way in Cloud Infrastructures?
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We use Cloudstack for our public cloud offering...

We enable at least a nominal amount of swap at the OS level in our Linux templates. This resides local to the VM. That is what you're referring to, correct?

To help you with your remaining questions, I'd need to understand your existing hardware/platform setup and what resources you have available to you. E.g. what types of servers, storage, storage tiers, etc.?

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You're right, I was referring to swap space inside the VM. I updated the question to reflect that. We have several storage options available (cheap FC SAN, expensive enterprise NAS). More important than which storage to use is for us, what benefit the user has if we offer him swap space. Also if we don't offer swap space, will the user just use some available storage to create swap while the performance of the swap then might not be optimal? – Florian Feldhaus Dec 3 '12 at 10:27

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