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    KVM Snapshot/Backup Script

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    kvm snapshots qcow2 linux virtualization
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    • RomoR
      Romo @stacksofplates
      last edited by

      @stacksofplates I only did a ls -lh

      output of ls -lsh

      2.9G -rw-r--r--. 1 root root 2.9G Oct 26 17:39 centos7-clone.qcow2
      1.1G -rw-r--r--. 1 root root  26G Feb  8 15:35 centos-7.qcow2
      
      stacksofplatesS 1 Reply Last reply Reply Quote 0
      • stacksofplatesS
        stacksofplates @Romo
        last edited by

        @Romo said in KVM Snapshot/Backup Script:

        I use this to create my image and the use virt-manager to finish the install

        qemu-img create -f qcow2 -o preallocation=metadata centos-7.qcow2 25G
        

        I preallocated the original template, and then when I clone with Virt-Manager or cli I don't usually change it after. I did some tests and didn't see any difference between running the preallocation on the clone and not. I'm not sure if it copies the preallocation flag when you clone, but like I said, I haven't seen much of a read/write difference.

        1 Reply Last reply Reply Quote 0
        • stacksofplatesS
          stacksofplates @Romo
          last edited by

          @Romo said in KVM Snapshot/Backup Script:

          @stacksofplates I only did a ls -lh

          output of ls -lsh

          2.9G -rw-r--r--. 1 root root 2.9G Oct 26 17:39 centos7-clone.qcow2
          1.1G -rw-r--r--. 1 root root  26G Feb  8 15:35 centos-7.qcow2
          

          Ya so it's thin provisioned. I wonder why it's taking so long. I don't think the disk speeds would make that much of a difference.

          1 Reply Last reply Reply Quote 2
          • stacksofplatesS
            stacksofplates
            last edited by

            What's your host specs? Mine is a DL380 G6. Dual 4 core Xeons and 96GB RAM. Don't think the RAM would have much to do with it. I had 24 originally and I'm pretty sure it cloned at the same speed.

            RomoR 1 Reply Last reply Reply Quote 0
            • RomoR
              Romo @stacksofplates
              last edited by

              @stacksofplates said in KVM Snapshot/Backup Script:

              What's your host specs? Mine is a DL380 G6. Dual 4 core Xeons and 96GB RAM. Don't think the RAM would have much to do with it. I had 24 originally and I'm pretty sure it cloned at the same speed.

              Its tiny 😃

              ML110 G7 8GB RAM , Single 4 core Xeon

              stacksofplatesS 1 Reply Last reply Reply Quote 0
              • stacksofplatesS
                stacksofplates @Romo
                last edited by

                @Romo said in KVM Snapshot/Backup Script:

                @stacksofplates said in KVM Snapshot/Backup Script:

                What's your host specs? Mine is a DL380 G6. Dual 4 core Xeons and 96GB RAM. Don't think the RAM would have much to do with it. I had 24 originally and I'm pretty sure it cloned at the same speed.

                Its tiny 😃

                ML110 G7 8GB RAM , Single 4 core Xeon

                Hmm. Do you have anything else running while you clone? You would think 4 cores would be enough as long as you're not way over provisioned.

                RomoR 1 Reply Last reply Reply Quote 0
                • RomoR
                  Romo @stacksofplates
                  last edited by

                  @stacksofplates said in KVM Snapshot/Backup Script:

                  @Romo said in KVM Snapshot/Backup Script:

                  @stacksofplates said in KVM Snapshot/Backup Script:

                  What's your host specs? Mine is a DL380 G6. Dual 4 core Xeons and 96GB RAM. Don't think the RAM would have much to do with it. I had 24 originally and I'm pretty sure it cloned at the same speed.

                  Its tiny 😃

                  ML110 G7 8GB RAM , Single 4 core Xeon

                  Hmm. Do you have anything else running while you clone? You would think 4 cores would be enough as long as you're not way over provisioned.

                  3 vms

                  virsh # list 
                   Id    Name                           State
                  ----------------------------------------------------
                   111   FreePBX                        running
                   144   rocket-chat                    running
                   160   ubt-ans-ininja                 running
                  

                  This is a clone on the centos image.

                  [root@kvm2 ~]# virt-clone -o centos-7 -n clone-test -f /vmrepo/clone-test.qcow2
                  Allocating 'clone-test.qcow2'                                                  |  25 GB  00:00:33     
                  
                  Clone 'clone-test' created successfully.
                  
                  stacksofplatesS 1 Reply Last reply Reply Quote 0
                  • stacksofplatesS
                    stacksofplates @Romo
                    last edited by

                    @Romo said in KVM Snapshot/Backup Script:

                    @stacksofplates said in KVM Snapshot/Backup Script:

                    @Romo said in KVM Snapshot/Backup Script:

                    @stacksofplates said in KVM Snapshot/Backup Script:

                    What's your host specs? Mine is a DL380 G6. Dual 4 core Xeons and 96GB RAM. Don't think the RAM would have much to do with it. I had 24 originally and I'm pretty sure it cloned at the same speed.

                    Its tiny 😃

                    ML110 G7 8GB RAM , Single 4 core Xeon

                    Hmm. Do you have anything else running while you clone? You would think 4 cores would be enough as long as you're not way over provisioned.

                    3 vms

                    virsh # list 
                     Id    Name                           State
                    ----------------------------------------------------
                     111   FreePBX                        running
                     144   rocket-chat                    running
                     160   ubt-ans-ininja                 running
                    

                    This is a clone on the centos image.

                    [root@kvm2 ~]# virt-clone -o centos-7 -n clone-test -f /vmrepo/clone-test.qcow2
                    Allocating 'clone-test.qcow2'                                                  |  25 GB  00:00:33     
                    
                    Clone 'clone-test' created successfully.
                    

                    Maybe it is hw limitations. I'm not sure. Still, 33 seconds is much faster than building by hand 😛

                    RomoR 1 Reply Last reply Reply Quote 1
                    • RomoR
                      Romo @stacksofplates
                      last edited by

                      @stacksofplates yeah it must be my hardware, and indeed it is way faster than building by hand. I will still be jealous of your cloning times =).

                      stacksofplatesS 1 Reply Last reply Reply Quote 1
                      • stacksofplatesS
                        stacksofplates @Romo
                        last edited by

                        @Romo said in KVM Snapshot/Backup Script:

                        @stacksofplates yeah it must be my hardware, and indeed it is way faster than building by hand. I will still be jealous of your cloning times =).

                        Oh mine is nothing. Google can spin up thousands with Kubernetes in seconds. That's something to be jealous of.

                        RomoR 1 Reply Last reply Reply Quote 2
                        • RomoR
                          Romo @stacksofplates
                          last edited by

                          @stacksofplates said in KVM Snapshot/Backup Script:

                          @Romo said in KVM Snapshot/Backup Script:

                          @stacksofplates yeah it must be my hardware, and indeed it is way faster than building by hand. I will still be jealous of your cloning times =).

                          Oh mine is nothing. Google can spin up thousands with Kubernetes in seconds. That's something to be jealous of.

                          But they spin up containers don't they.

                          stacksofplatesS 1 Reply Last reply Reply Quote 1
                          • stacksofplatesS
                            stacksofplates @Romo
                            last edited by

                            @Romo said in KVM Snapshot/Backup Script:

                            @stacksofplates said in KVM Snapshot/Backup Script:

                            @Romo said in KVM Snapshot/Backup Script:

                            @stacksofplates yeah it must be my hardware, and indeed it is way faster than building by hand. I will still be jealous of your cloning times =).

                            Oh mine is nothing. Google can spin up thousands with Kubernetes in seconds. That's something to be jealous of.

                            But they spin up containers don't they.

                            True, good point but I would think it's relative. For example I could probably only spin up a handful in a few seconds. With their equipment they have to be able to spin up a ton of full VMs pretty quickly.

                            Plus there are the really trimmed down cloud versions of these OSs that spin up even faster.

                            1 Reply Last reply Reply Quote 1
                            • A
                              Alex Sage
                              last edited by

                              Thanks.

                              1 Reply Last reply Reply Quote 0
                              • ntoxicatorN
                                ntoxicator
                                last edited by

                                @stacksofplates

                                Very nice!

                                Question:

                                I'm looking to setup a oVIRT engine + node setup. I think this script will help, as Ideally, i do not want to store my snapshots on the primary VM storage (iSCSI). Would rather have them be saved to a secondary storage location (NFS) location.

                                how would I modify your script to specify another storage location? I do not see the argument where to modify the snap location

                                matteo nunziatiM 1 Reply Last reply Reply Quote 0
                                • matteo nunziatiM
                                  matteo nunziati @ntoxicator
                                  last edited by

                                  @ntoxicator I think he is grabbing a temp snapshot and then he tar.gz's the snap to the destination (e.g. an NFS mount). Then the snap is destroyed, otherwise you get worse and worse on performance.

                                  stacksofplatesS 1 Reply Last reply Reply Quote 2
                                  • stacksofplatesS
                                    stacksofplates @matteo nunziati
                                    last edited by stacksofplates

                                    @matteo-nunziati said in KVM Snapshot/Backup Script:

                                    @ntoxicator I think he is grabbing a temp snapshot and then he tar.gz's the snap to the destination (e.g. an NFS mount). Then the snap is destroyed, otherwise you get worse and worse on performance.

                                    This is correct. The snapshot only lives long enough to copy the disk to the specified location and is then merged back into the original disk. Here's what it would look like using a disk called vm-test.qcow2

                                    vm-test.qcow2 (base) < ----  vm-test-snap.qcow2 (overlay)
                                    

                                    When the snapshot is taken, writes are directed to the overlay file (vm-test-snap.qcow2) and reads are done from the base (vm-test.qcow2). The script then copies the base image to whatever storage you want. Once it's copied, the overlay is blockcommitted to the base disk and the VM is pivoted back to the base disk. Then it just deletes the snapshot and the overlay file.

                                    The snapshots shouldn't be very large at all. If there is nothing going on, the size could be kilobytes until it's blockcommitted.

                                    ntoxicatorN 1 Reply Last reply Reply Quote 1
                                    • ntoxicatorN
                                      ntoxicator @stacksofplates
                                      last edited by

                                      @stacksofplates

                                      Thank you for clarification.

                                      Once snap is stored / saved to location - can a full VM be recreated from that snap taken?

                                      What if the original VM disk (.qcow2) was destroyed or lost (say failure). Could the VM be recreated from that said snap taken? (Restored from snap save location)

                                      Essentially, Trying to find a way to completely backup KVM's within a production environment. As most snapshots will take larger space on the originating VM storage location. Have snaps offloaded to a NFS Share -- less expensive storage than the originating VM location

                                      Snaps be stored for life on the NFS - and can restore from snapshot or roll-back. As would like to use these Snapshots for production within or for Xen Desktop....

                                      As trying to find a production replacement for XenServer - due to storage virtual disk limitations. can only have 2TB vdisk assigned to any VM at any time. The storage repository or iSCSI LUN can be of any size, but am capp'd at 2TB for a VM disk...

                                      its love at first sight for Xen Orchestra integration for XS (Snapshots, rolling/delta, etc) But the storage limitation kills me..

                                      Sorry for gettint off topic! Just trying to show my proof of concept and need for said snapshot script.

                                      RomoR stacksofplatesS matteo nunziatiM 3 Replies Last reply Reply Quote 0
                                      • RomoR
                                        Romo @ntoxicator
                                        last edited by

                                        What if the original VM disk (.qcow2) was destroyed or lost (say failure). Could the VM be recreated from that said snap taken? (Restored from snap save location)

                                        Snapshots would not work if the base file is written to or doesn't exist.

                                        As @stacksofplates responded

                                        the snapshot only lives long enough to copy the disk to the specified location and is then merged back into the original disk. Here's what it would look like using a disk called vm-test.qcow2.

                                        Think of the process as cloning the original disk without shutting down the vm, the snapshot is just temporal ceases to exist once the original file is copied.

                                        As most snapshots will take larger space on the originating VM storage location. Have snaps offloaded to a NFS Share -- less expensive storage than the originating VM location

                                        1 Reply Last reply Reply Quote 1
                                        • stacksofplatesS
                                          stacksofplates
                                          last edited by

                                          Right, we aren't copying the snapshot, we are copying the disk before the snapshot was taken. Then the snapshot is blockcommitted back into the original.

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                                          • stacksofplatesS
                                            stacksofplates @ntoxicator
                                            last edited by

                                            @ntoxicator said in KVM Snapshot/Backup Script:

                                            What if the original VM disk (.qcow2) was destroyed or lost (say failure). Could the VM be recreated from that said snap taken? (Restored from snap save location)

                                            Yes, the saved disk (not the snapshot) can be copied back to the normal image directory and you can start the VM again.

                                            This is assuming you are using images and not block storage. If you've just mounted the LUN through the hypervisor and are using block storage, this won't work. If you've mounted the LUN to a directory and created a file system on it to store images, then this will work.

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