Understanding Snapshots, SmartGuard and Time Machine

Discussion in 'Installation and Configuration' started by AndrewJ7, Jun 18, 2020.

  1. AndrewJ7

    AndrewJ7 Bit Poster

    I want to make sure I understand what is happening with these features - unfortunately, many links I try and follow just lead to a "This content is outdated" message.

    Snapshots are just point-in-time copy of a VM's state when it is taken. So, for example, before making major changes to a VM I can create a snapshot and if it all goes wrong with the current state, then I can revert back. Snapshots, once made, do not change if never loaded and thus Time Machine does not need to back it up.

    SmartGuard is a way of automating the creation of Snapshots to aid back up with Time Machine. On a regular basis, it will create a snapshot and using the Snapshot manager I could see (date and timestamped): Snapshot 1, Snapshot 2, Snapshot 3, Current State. Snapshot 1 through Snapshot 3 never change if I don't load them so Time Machine doesn't need to back them up. Current State is the VM I am currently working on, does change, and does get saved by Time Machine.

    The reported size of the .PVM file includes all snapshots and thus increases in size as (a) a new snapshot is created; (b) work goes on in Current State. The size of Current State is the actual reported disk size usage in the VM itself (e.g. C: if a Windows VM) plus I suppose some Parallels management size.

    Deleting a Snapshot actually just merges it into the next 'higher' Snapshot. So from the above example, Deleting Snapshot 1, merges it into Snapshot 2. Time Machine will then backup this merged Snapshot once (because it has changed) as well as Current State. Deleting the last Snapshot merges it into Current State. When all I have is Current State, the size of the .PVM should be close to the actual reported disk size in the VM itself. Thus, deleting Snapshots gradually reduces the size of the .PVM file.

    Have I misunderstood anything or is there anything worth adding?


  2. Maria@Parallels

    Maria@Parallels Parallels Team

    Hi Andrew, you're right and understand everything about Snapshots, Smart Guard and Time Machine correctly.
    You can also check the actual KB articles:
    https://kb.parallels.com/5688 - about the SmartGuatrd
    https://kb.parallels.com/5691 - about the Snaphots.

    If you have any additional questions please do not hesitate to let us know.
  3. AndrewJ7

    AndrewJ7 Bit Poster

    Thanks MarĂ­a.
    Maria@Parallels likes this.
  4. GeorgeL9

    GeorgeL9 Bit Poster

    If i am using SmartGuard, should i exclude the VM from Time Machine?
  5. AndrewJ7

    AndrewJ7 Bit Poster

    If you want to backup your VM with Time machine, do not exclude it. If you want to back it up some other way, then exclude it. Smart guard automatically creates snapshots periodically so that Time Machine doesn't need to back up an ever increasing VM. When a snapshot is created, it will be backed up once by TM and then, because it never changes, it will be ignored. Only the current snapshot is regularly backed up by TM. When smart guard deletes a snapshot (i.e. merges into the next 'later' one, that changed snapshot will be backed up once by TM - unless of course it's been merged into the current snapshot which is always backed up.

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