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  • Confusion about snapshots

    I know how to do a snapshot of the VM and I see the files it creates. My questions are the following:

    1) Does the snapshot files actually contain ALL of the data of the VM? The size of the snapshot is significantly smaller.

    2) Aside from using some of the backup software that I have seen in other posts, e.g. CA, PHD, Vizioncore, etc., is there any other way to copy those snapshots off to Windows server?

    3) If I was to install VMWare on a different box, could I recover that VM and all of its data by copying back the snapshot files and restoring them?

    Thanks!

  • #2
    Re: Confusion about snapshots

    Originally posted by here4real View Post
    1) Does the snapshot files actually contain ALL of the data of the VM? The size of the snapshot is significantly smaller.
    Nope. A snapshot is a point in time representation of a virtual machine. It contains active memory contents and diffs to virtual hard disk. When a snapshot is restored, the contents of vhd and snapshot are merged to re-create disk state. Memory state is stored entirely in the snapshot. If the virtual machine is not running, the snapshot contains only vhd diffs. There might be some compression involved as well.

    3) If I was to install VMWare on a different box, could I recover that VM and all of its data by copying back the snapshot files and restoring them?
    Yes, but then you would have duplicate computer names and IP addresses in your network. Think carefully what it might cause. In R&D environment such situation might be OK.

    -vP

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    • #3
      Re: Confusion about snapshots

      I actually wrote a big long post about snapshots on here somewhere if I recall, about entirely how it works, including the two-stage thing.

      Have a search through my posts for snapshot and see if you can find it.. else i'll try and remember later
      Please do show your appreciation to those who assist you by leaving Rep Point https://www.petri.com/forums/core/im.../icon_beer.gif

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      • #4
        Re: Confusion about snapshots

        Thanks!

        I just want to make sure I have this straight. If I could copy off the vmdk (original), vswp and vmsn created by the snapshot (I don't see a vmem file) and put them on a separate vmware box, I would completely recover the entire VM as of the time of that snapshot? Or do other files also need copying? I see it started creating a new vmdk file. I assume that is changes to the disk AFTER the snapshot?

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        • #5
          Re: Confusion about snapshots

          What I am trying to get to is a disaster recovery solution that is non-proprietary. We are currently using Arcserve but it backs the files up in an Arcserve format. Recovery would require installing Arcserve BEFORE getting the files back. I want to start from an assumption that I have a functioning VMWare box and just restore the VM.

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          • #6
            Re: Confusion about snapshots

            no. you can't copy the snapshot file and have it work.

            what happens when you crete a snapshot is vmware pauses the guest for a microsecond and creates a new vsnp file (or whatever it's called.)
            anything NEW writes into that file

            When you merge the snapshot, it pauses the machine again, makes a second vnsp file, and starts writing more changes into that.
            While this is happening, it merges down the initial snapshot file
            Then, it pauses the machine for a moment, to write the changes from the SECOND snapshot, to make one full image.

            and of course, if you delete rather than merge the snapshot, all changes are lost.


            the way something like vizioncore's vRanger product works is follows:

            1. create snapshot
            (this removes the filesystem lock from the actual vmdk file)
            2. copy base VMDK File elsewhere
            3. Merge snapshot (as above)

            for a free solution, you could check out VISBU
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            • #7
              Re: Confusion about snapshots

              Thanks. This was a BIG help. PHD advantage is that the backup is non-proprietary. vRanger worked VERY easily.

              This has led to a follow question which is backing up the ESX server itself (without the VMs). Any suggestions?

              Once again, I am thinking in terms of DR and getting a server and VMs back up and running as quickly as possible.

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              • #8
                Re: Confusion about snapshots

                uhm, you'd need to backup the configuration files more than the OS really.. doesn't take an insane amount of time to install ESX - it's almost as quick to install as to restore.


                Exactly which ones, I forget off the top of my head


                take a look at this:
                http://communities.vmware.com/thread/169136

                I've also found yellowbricks (http://www.yellow-bricks.com/) to be a very good resource on several occasions, mainly for management and things like that
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