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Project Fargo aka VMFork and TPS?

Duncan Epping · Nov 11, 2014 ·

I received some questions this week around how VMFork (aka Instant Clone) will work when TPS is disabled in the future, already answered some questions in comments but figured this would be easier to google. First of all, I would like to point out that in future versions TPS will not be globally disabled, but rather it will disabled for inter-VM page collapsing. Within the VM though pages will be collapsed as normal and the way it works is that each virtual machine configuration will contain a salt and all virtual machines with the same salt will share pages… However, each virtual machine by default will have a unique salt. Now this is where a VMFork’ed virtual machine will differ in the future.

VMFork’ed virtual machines in the future will share the salt, which means that “VMFork groups” can be considered a security domain and pages will be shared between all of these VMs. In other words, the parent and all of its children have the same salt and will share pages (see sched.mem.pshare.salt). If you have a different parent then pages between those VMFork Groups (both parents and its children) will not be shared.

Related

Management & Automation, Server, Various devops, project fargo, vmfork

Reader Interactions

Comments

  1. Justin Adams says

    11 November, 2014 at 15:43

    Duncan, can you define a salt please?

    • John Nicholson. says

      14 November, 2014 at 17:28

      Basically something you add that is random so that you can not brute force hash collisions.

  2. Timo Sugliani says

    11 November, 2014 at 17:22

    Hi Justin,

    This should depict it well: http://en.wikipedia.org/wiki/Salt_(cryptography)

    Regards,

  3. Simon Sparks says

    2 February, 2015 at 12:12

    How does this relate to Linked Clones deployed by vCloud Director ?

    Will all the linked clones and all the shadow copies of the original Virtual Machine / Golden Snapshot share the same salt ?

    • Duncan Epping says

      2 February, 2015 at 13:47

      Have not seen any details about this for vCloud Director based environments.

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About the author

Duncan Epping is a Chief Technologist in the Office of CTO of the Cloud Platform BU at VMware. He is a VCDX (# 007), the author of the "vSAN Deep Dive", the “vSphere Clustering Technical Deep Dive” series, and the host of the "Unexplored Territory" podcast.

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