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    CBT: the thread to centralize your feedback

    Scheduled Pinned Locked Moved Backup
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    • R Offline
      rtjdamen @flakpyro
      last edited by

      @flakpyro no on my end there is no difference for nfs or iscsi on XOA backups, we only had this issue with Alike Backup, my assumption was this would be the case in XOA as well, but not at this time.

      What i found out is that one of my vms facing this issue has 2 disks, both on a different SR, i am moving one of the disks to the same SR and check tomorrow (tonight will be a full after migrating) if this is still the case there.

      The other vm we face this issue on is has both disks on the same SR so that cannot be the case there. keep u posted on the results.

      florentF 1 Reply Last reply Reply Quote 0
      • florentF Offline
        florent Vates 🪐 XO Team @rtjdamen
        last edited by florent

        @rtjdamen we found a clue with @Bastien-Nollet : there was a race condition between the timeframe allowed to enable CBT and the snapshot, leading to a snapshot taken before CBT , thus failing to compute correctly the list of changed block at the next backup

        The fix is deployed, and we'll see this night. If everything goes well, this night will be a full, but the disks will keep CBT enabled. And the next night, we'll have delta

        if everything is ok, it will be released in a second patch ( 5.100.2 )

        R 1 Reply Last reply Reply Quote 1
        • R Offline
          rtjdamen @florent
          last edited by

          @florent sounds like a plan! i will keep an eye on them and let u know the results!

          1 Reply Last reply Reply Quote 0
          • B Offline
            barwys
            last edited by

            Hi,
            I observed one issue with the backup process when the CBT is enabled. The case is showing when the VM has two disks on different SRs. When the backup tries to be taken, it fails, and the machine goes to a state where no other changes/reconfiguration is possible. It is not possible to disable CBT, move a disk to a different SR or create another backup. Sometimes after a failed backup the console access and machine are freezing. Everything works fine when all of the VM disks are on one SR.

            The logs from the first backup:
            SCR-20241113-jypa.png

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            • olivierlambertO Offline
              olivierlambert Vates 🪐 Co-Founder CEO
              last edited by

              Hi @barwys

              Can you provide more details? We need to know on which commit or XOA version you are 🙂

              B 1 Reply Last reply Reply Quote 0
              • B Offline
                barwys @olivierlambert
                last edited by

                @olivierlambert Xen Orchestra, commit 804af
                Both SRs are the shared storage by Fibre Channels connection (multipathing enabled). I tested on the Windows or Linux guest system as well. XenTools respectively 9.4.0/9.3.3 and 8.4.0-1 respectively.

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                • olivierlambertO Offline
                  olivierlambert Vates 🪐 Co-Founder CEO
                  last edited by

                  This commit is already a week old, please update to the latest one, rebuild and try again

                  B 1 Reply Last reply Reply Quote 0
                  • B Offline
                    barwys @olivierlambert
                    last edited by

                    Hello @olivierlambert,
                    After upgrading to commit 05c4e, I cannot reproduce this issue again. It seems to work much better.
                    Thanks

                    1 Reply Last reply Reply Quote 1
                    • olivierlambertO Offline
                      olivierlambert Vates 🪐 Co-Founder CEO
                      last edited by

                      Great! Please remember to always be on latest commit before reporting a problem, as you can see the code base is evolving fast 😉

                      F 1 Reply Last reply Reply Quote 0
                      • F Offline
                        flakpyro @olivierlambert
                        last edited by

                        @olivierlambert Unfortunately after updating to 5.100.2 (XOA and Proxies) i am still running into XOA backups falling back to full after preforming a VM migration between two hosts within a pool when snapshot deletion is enabled. This doesnt happen if the snapshot is retained.

                        My test setup:
                        Servers: 2 x HP DL325 Gen 10 AMD Epyc Servers
                        Storage: TrueNAS Mini R running TrueNAS Scale 24.10 serving an NFS SR shared between both servers.
                        All VMs running on the same shared SR on the TrueNAS.

                        Scenario:
                        VM 1 Migrated from Host A to Host B
                        VM 2 Migrated from Host B to Host A

                        Running a CBT with Snapshot delete backup after migration the VM between hosts while they remain on the same shared SR results in the error:

                        "Can't do delta with this vdi, transfer will be a full"
                        "Can't do delta, will try to get a full stream"

                        Full log and screenshot of the error:
                        2024-11-14T19_20_40.383Z - backup NG.json.txt

                        Screenshot_20241114_132811.png

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                        • olivierlambertO Offline
                          olivierlambert Vates 🪐 Co-Founder CEO
                          last edited by

                          Sadly you are the only one we know we this problem that we cannot reproduce 😢

                          I suppose we already checked that the VDI UUID doesn't change after the migration right?

                          F 1 Reply Last reply Reply Quote 0
                          • F Offline
                            flakpyro @olivierlambert
                            last edited by flakpyro

                            @olivierlambert Yeah we did confirm the UUID does not change. These are VMs that were imported from VMware using the XOA wizard if that makes any difference.

                            The only other pool i have i could try on would be our production pool which is using CBT but is not removing the snapshot.

                            However if i migrate a VM between hosts on that pool and run a backup job i see this on the pool masters SMLog

                            Nov 14 21:06:50 xcpng-prd-03 SM: [3980818] Size of bitmap: 491520
Nov 14 21:06:50 xcpng-prd-03 SM: [3980818] lock: acquired /var/lock/sm/c63f7214-c1ef-4fc3-b174-cb78dffcbaa6/cbtlog
Nov 14 21:06:50 xcpng-prd-03 SM: [3980818] ['/usr/sbin/cbt-util', 'get', '-n', '/var/run/sr-mount/16e4ecd2-583e-e2a0-5d3d-8e53ae9c1429/c63f7214-c1ef-4fc3-b174-cb78dffcbaa6.cbtlog', '-c']
Nov 14 21:06:50 xcpng-prd-03 SM: [3980818]   pread SUCCESS
Nov 14 21:06:50 xcpng-prd-03 SM: [3980818] lock: released /var/lock/sm/c63f7214-c1ef-4fc3-b174-cb78dffcbaa6/cbtlog
Nov 14 21:06:50 xcpng-prd-03 SM: [3980818] Raising exception [460, Failed to calculate changed blocks for given VDIs. [opterr=Source and target VDI are unrelated]]
Nov 14 21:06:50 xcpng-prd-03 SM: [3980818] ***** generic exception: vdi_list_changed_blocks: EXCEPTION <class 'xs_errors.SROSError'>, Failed to calculate changed blocks for given VDIs. [opterr=Source and target VDI are unrelated]
Nov 14 21:06:50 xcpng-prd-03 SM: [3980818]   File "/opt/xensource/sm/SRCommand.py", line 111, in run
Nov 14 21:06:50 xcpng-prd-03 SM: [3980818]     return self._run_locked(sr)
Nov 14 21:06:50 xcpng-prd-03 SM: [3980818]   File "/opt/xensource/sm/SRCommand.py", line 161, in _run_locked
Nov 14 21:06:50 xcpng-prd-03 SM: [3980818]     rv = self._run(sr, target)
Nov 14 21:06:50 xcpng-prd-03 SM: [3980818]   File "/opt/xensource/sm/SRCommand.py", line 326, in _run
Nov 14 21:06:50 xcpng-prd-03 SM: [3980818]     return target.list_changed_blocks()
Nov 14 21:06:50 xcpng-prd-03 SM: [3980818]   File "/opt/xensource/sm/VDI.py", line 757, in list_changed_blocks
Nov 14 21:06:50 xcpng-prd-03 SM: [3980818]     "Source and target VDI are unrelated")
Nov 14 21:06:50 xcpng-prd-03 SM: [3980818]
Nov 14 21:06:50 xcpng-prd-03 SM: [3980818] ***** NFS VHD: EXCEPTION <class 'xs_errors.SROSError'>, Failed to calculate changed blocks for given VDIs. [opterr=Source and target VDI are unrelated]
Nov 14 21:06:50 xcpng-prd-03 SM: [3980818]   File "/opt/xensource/sm/SRCommand.py", line 385, in run
Nov 14 21:06:50 xcpng-prd-03 SM: [3980818]     ret = cmd.run(sr)
Nov 14 21:06:50 xcpng-prd-03 SM: [3980818]   File "/opt/xensource/sm/SRCommand.py", line 111, in run
Nov 14 21:06:50 xcpng-prd-03 SM: [3980818]     return self._run_locked(sr)
Nov 14 21:06:50 xcpng-prd-03 SM: [3980818]   File "/opt/xensource/sm/SRCommand.py", line 161, in _run_locked
--
Nov 14 21:07:05 xcpng-prd-03 SM: [3981883] Size of bitmap: 25165824
Nov 14 21:07:05 xcpng-prd-03 SM: [3981883] lock: acquired /var/lock/sm/90202d5b-8016-49a3-92dd-4790a2edaa41/cbtlog
Nov 14 21:07:05 xcpng-prd-03 SM: [3981883] ['/usr/sbin/cbt-util', 'get', '-n', '/var/run/sr-mount/16e4ecd2-583e-e2a0-5d3d-8e53ae9c1429/90202d5b-8016-49a3-92dd-4790a2edaa41.cbtlog', '-c']
Nov 14 21:07:05 xcpng-prd-03 SM: [3981883]   pread SUCCESS
Nov 14 21:07:05 xcpng-prd-03 SM: [3981883] lock: released /var/lock/sm/90202d5b-8016-49a3-92dd-4790a2edaa41/cbtlog
Nov 14 21:07:05 xcpng-prd-03 SM: [3981883] Raising exception [460, Failed to calculate changed blocks for given VDIs. [opterr=Source and target VDI are unrelated]]
Nov 14 21:07:05 xcpng-prd-03 SM: [3981883] ***** generic exception: vdi_list_changed_blocks: EXCEPTION <class 'xs_errors.SROSError'>, Failed to calculate changed blocks for given VDIs. [opterr=Source and target VDI are unrelated]
Nov 14 21:07:05 xcpng-prd-03 SM: [3981883]   File "/opt/xensource/sm/SRCommand.py", line 111, in run
Nov 14 21:07:05 xcpng-prd-03 SM: [3981883]     return self._run_locked(sr)
Nov 14 21:07:05 xcpng-prd-03 SM: [3981883]   File "/opt/xensource/sm/SRCommand.py", line 161, in _run_locked
Nov 14 21:07:05 xcpng-prd-03 SM: [3981883]     rv = self._run(sr, target)
Nov 14 21:07:05 xcpng-prd-03 SM: [3981883]   File "/opt/xensource/sm/SRCommand.py", line 326, in _run
Nov 14 21:07:05 xcpng-prd-03 SM: [3981883]     return target.list_changed_blocks()
Nov 14 21:07:05 xcpng-prd-03 SM: [3981883]   File "/opt/xensource/sm/VDI.py", line 757, in list_changed_blocks
Nov 14 21:07:05 xcpng-prd-03 SM: [3981883]     "Source and target VDI are unrelated")
Nov 14 21:07:05 xcpng-prd-03 SM: [3981883]
Nov 14 21:07:05 xcpng-prd-03 SM: [3981883] ***** NFS VHD: EXCEPTION <class 'xs_errors.SROSError'>, Failed to calculate changed blocks for given VDIs. [opterr=Source and target VDI are unrelated]
Nov 14 21:07:05 xcpng-prd-03 SM: [3981883]   File "/opt/xensource/sm/SRCommand.py", line 385, in run
Nov 14 21:07:05 xcpng-prd-03 SM: [3981883]     ret = cmd.run(sr)
Nov 14 21:07:05 xcpng-prd-03 SM: [3981883]   File "/opt/xensource/sm/SRCommand.py", line 111, in run
Nov 14 21:07:05 xcpng-prd-03 SM: [3981883]     return self._run_locked(sr)
Nov 14 21:07:05 xcpng-prd-03 SM: [3981883]   File "/opt/xensource/sm/SRCommand.py", line 161, in _run_locked

                            This goes away after the the initial backup run after the VM migration and all runs after result in nothing in the SMLog. Because i am not removing the snapshot the backup still runs as a delta however this leads me to believe if i enabled snapshot delete on that pool i would run into the same issue and a full backup would run instead.

                            I'm not sure what i would be doing that's unique to cause this. TestLab is NFS4 on a TrueNAS and Production is NFS3 on a Pure X20 array.

                            I will soon be able to test this on our DR site pool but we are currently waiting on hardware for that to arrive.

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                            • olivierlambertO Offline
                              olivierlambert Vates 🪐 Co-Founder CEO
                              last edited by

                              I have no idea why you are the only one to have this issue, which is why it's weird 😄

                              F 1 Reply Last reply Reply Quote 0
                              • F Offline
                                flakpyro @olivierlambert
                                last edited by flakpyro

                                @olivierlambert So today i installed the latest round of updates on the test pool which moved all the VMs back and forth during a rolling pool update. I then let everything sit for a couple hours then ran the backup job and this time it did not throw any errors. So thats even more confusing.

                                Perhaps its because i am kicking off a backup job immediately after migrating the VMs? As a test i am going to move them around again now, wait an hour then attempt to run the job.

                                Edit: Waiting did not seem to help. Running the job manually again resulted in a full being run again with the same
                                Can't do delta with this vdi, transfer will be a full
                                Can't do delta, will try to get a full stream

                                F 1 Reply Last reply Reply Quote 0
                                • F Offline
                                  flakpyro @flakpyro
                                  last edited by

                                  SMLog output on the test pool looks the same as production pool after a manual VM migration:

                                  I did also double check that the VM UUID does not change after the migration.

                                  Nov 15 13:59:40 xcpng-test-01 SM: [277865] lock: opening lock file /var/lock/sm/8b0ee29e-7cbe-4e15-bd13-330a974fde2a/cbtlog
Nov 15 13:59:40 xcpng-test-01 SM: [277865] lock: acquired /var/lock/sm/8b0ee29e-7cbe-4e15-bd13-330a974fde2a/cbtlog
Nov 15 13:59:40 xcpng-test-01 SM: [277865] ['/usr/sbin/cbt-util', 'get', '-n', '/var/run/sr-mount/45e457aa-16f8-41e0-d03d-8201e69638be/8b0ee29e-7cbe-4e15-bd13-330a974fde2a.cbtlog', '-c']
Nov 15 13:59:40 xcpng-test-01 SM: [277865]   pread SUCCESS
Nov 15 13:59:40 xcpng-test-01 SM: [277865] lock: released /var/lock/sm/8b0ee29e-7cbe-4e15-bd13-330a974fde2a/cbtlog
Nov 15 13:59:40 xcpng-test-01 SM: [277865] Raising exception [460, Failed to calculate changed blocks for given VDIs. [opterr=Source and target VDI are unrelated]]
Nov 15 13:59:40 xcpng-test-01 SM: [277865] ***** generic exception: vdi_list_changed_blocks: EXCEPTION <class 'xs_errors.SROSError'>, Failed to calculate changed blocks for given VDIs. [opterr=Source and target VDI are unrelated]
Nov 15 13:59:40 xcpng-test-01 SM: [277865]   File "/opt/xensource/sm/SRCommand.py", line 111, in run
Nov 15 13:59:40 xcpng-test-01 SM: [277865]     return self._run_locked(sr)
Nov 15 13:59:40 xcpng-test-01 SM: [277865]   File "/opt/xensource/sm/SRCommand.py", line 161, in _run_locked
Nov 15 13:59:40 xcpng-test-01 SM: [277865]     rv = self._run(sr, target)
Nov 15 13:59:40 xcpng-test-01 SM: [277865]   File "/opt/xensource/sm/SRCommand.py", line 326, in _run
Nov 15 13:59:40 xcpng-test-01 SM: [277865]     return target.list_changed_blocks()
Nov 15 13:59:40 xcpng-test-01 SM: [277865]   File "/opt/xensource/sm/VDI.py", line 757, in list_changed_blocks
Nov 15 13:59:40 xcpng-test-01 SM: [277865]     "Source and target VDI are unrelated")
Nov 15 13:59:40 xcpng-test-01 SM: [277865]
Nov 15 13:59:40 xcpng-test-01 SM: [277865] ***** NFS VHD: EXCEPTION <class 'xs_errors.SROSError'>, Failed to calculate changed blocks for given VDIs. [opterr=Source and target VDI are unrelated]
Nov 15 13:59:40 xcpng-test-01 SM: [277865]   File "/opt/xensource/sm/SRCommand.py", line 385, in run
Nov 15 13:59:40 xcpng-test-01 SM: [277865]     ret = cmd.run(sr)
Nov 15 13:59:40 xcpng-test-01 SM: [277865]   File "/opt/xensource/sm/SRCommand.py", line 111, in run
Nov 15 13:59:40 xcpng-test-01 SM: [277865]     return self._run_locked(sr)
Nov 15 13:59:40 xcpng-test-01 SM: [277865]   File "/opt/xensource/sm/SRCommand.py", line 161, in _run_locked
--
Nov 15 13:59:45 xcpng-test-01 SM: [278274] lock: opening lock file /var/lock/sm/fa7929aa-a39c-437d-9787-5218e9bcbc1a/cbtlog
Nov 15 13:59:45 xcpng-test-01 SM: [278274] lock: acquired /var/lock/sm/fa7929aa-a39c-437d-9787-5218e9bcbc1a/cbtlog
Nov 15 13:59:45 xcpng-test-01 SM: [278274] ['/usr/sbin/cbt-util', 'get', '-n', '/var/run/sr-mount/45e457aa-16f8-41e0-d03d-8201e69638be/fa7929aa-a39c-437d-9787-5218e9bcbc1a.cbtlog', '-c']
Nov 15 13:59:45 xcpng-test-01 SM: [278274]   pread SUCCESS
Nov 15 13:59:45 xcpng-test-01 SM: [278274] lock: released /var/lock/sm/fa7929aa-a39c-437d-9787-5218e9bcbc1a/cbtlog
Nov 15 13:59:45 xcpng-test-01 SM: [278274] Raising exception [460, Failed to calculate changed blocks for given VDIs. [opterr=Source and target VDI are unrelated]]
Nov 15 13:59:45 xcpng-test-01 SM: [278274] ***** generic exception: vdi_list_changed_blocks: EXCEPTION <class 'xs_errors.SROSError'>, Failed to calculate changed blocks for given VDIs. [opterr=Source and target VDI are unrelated]
Nov 15 13:59:45 xcpng-test-01 SM: [278274]   File "/opt/xensource/sm/SRCommand.py", line 111, in run
Nov 15 13:59:45 xcpng-test-01 SM: [278274]     return self._run_locked(sr)
Nov 15 13:59:45 xcpng-test-01 SM: [278274]   File "/opt/xensource/sm/SRCommand.py", line 161, in _run_locked
Nov 15 13:59:45 xcpng-test-01 SM: [278274]     rv = self._run(sr, target)
Nov 15 13:59:45 xcpng-test-01 SM: [278274]   File "/opt/xensource/sm/SRCommand.py", line 326, in _run
Nov 15 13:59:45 xcpng-test-01 SM: [278274]     return target.list_changed_blocks()
Nov 15 13:59:45 xcpng-test-01 SM: [278274]   File "/opt/xensource/sm/VDI.py", line 757, in list_changed_blocks
Nov 15 13:59:45 xcpng-test-01 SM: [278274]     "Source and target VDI are unrelated")
Nov 15 13:59:45 xcpng-test-01 SM: [278274]
Nov 15 13:59:45 xcpng-test-01 SM: [278274] ***** NFS VHD: EXCEPTION <class 'xs_errors.SROSError'>, Failed to calculate changed blocks for given VDIs. [opterr=Source and target VDI are unrelated]
Nov 15 13:59:45 xcpng-test-01 SM: [278274]   File "/opt/xensource/sm/SRCommand.py", line 385, in run
Nov 15 13:59:45 xcpng-test-01 SM: [278274]     ret = cmd.run(sr)
Nov 15 13:59:45 xcpng-test-01 SM: [278274]   File "/opt/xensource/sm/SRCommand.py", line 111, in run
Nov 15 13:59:45 xcpng-test-01 SM: [278274]     return self._run_locked(sr)
Nov 15 13:59:45 xcpng-test-01 SM: [278274]   File "/opt/xensource/sm/SRCommand.py", line 161, in _run_locked
                                  F 1 Reply Last reply Reply Quote 0
                                  • F Offline
                                    flakpyro @flakpyro
                                    last edited by flakpyro

                                    @olivierlambert Im making progress getting to the bottom of this thanks to some documentation from XenServer about using cbt-util.

                                    You can use the cbt-util utility, which helps establish chain relationship. If the VDI snapshots are not linked by changed block metadata, you get errors like “SR_BACKEND_FAILURE_460”, “Failed to calculate changed blocks for given VDIs”, and “Source and target VDI are unrelated”.

Example usage of cbt-util:

 cbt-util get –c –n <name of cbt log file>

The -c option prints the child log file UUID.

                                    I cleared all CBT snapshots from my test VMs and run a full backup on each VM. Then ensured the CBT chain was consistent using cbt-util, the output was:

                                    [14:22 xcpng-test-01 45e457aa-16f8-41e0-d03d-8201e69638be]# cbt-util get -c -n 867063fc-4d86-420a-9ad2-dfe1749ecbc1.cbtlog 
1950d6a3-c6a9-4b0c-b79f-068dd44479cc

                                    After the backup was complete i then migrated the VM to the second host in the pool and ran the same command from both hosts:

                                    [14:26 xcpng-test-01 45e457aa-16f8-41e0-d03d-8201e69638be]# cbt-util get -c -n 867063fc-4d86-420a-9ad2-dfe1749ecbc1.cbtlog 
00000000-0000-0000-0000-000000000000

                                    And from the second host:

                                    [14:26 xcpng-test-02 45e457aa-16f8-41e0-d03d-8201e69638be]# cbt-util get -c -n 867063fc-4d86-420a-9ad2-dfe1749ecbc1.cbtlog 
00000000-0000-0000-0000-000000000000

                                    That clearly is the problem right there, question is, what is causing that to happen?

                                    After running another full the zero'd out cbtlog file is removed and a new one is created which will work fine until the VM is migrated again:

                                    [14:39 xcpng-test-01 45e457aa-16f8-41e0-d03d-8201e69638be]# cbt-util get -c -n 1eefb7bf-9dc3-4830-8352-441a77412576.cbtlog 
1950d6a3-c6a9-4b0c-b79f-068dd44479cc
                                    R 1 Reply Last reply Reply Quote 1
                                    • R Offline
                                      rtjdamen @flakpyro
                                      last edited by

                                      @flakpyro i can't reproduce this on our end, after migration within pool on the same storage pool the cbt is preserved. When i migrate to a different storage pool the cbt is reset.

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                                      • F Offline
                                        flakpyro @rtjdamen
                                        last edited by

                                        @rtjdamen interesting, this is with iSCSI (block) or with an NFS SR?

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                                        • R Offline
                                          rtjdamen @flakpyro
                                          last edited by

                                          @flakpyro both scenarios

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                                          • F Offline
                                            flakpyro @rtjdamen
                                            last edited by

                                            @rtjdamen Hmm very strange.

                                            The only thing i can think of is that this maybe due to the fact these VMs were imported from VMware.

                                            Next week i can try creating a brand new NFSv3 SR (Since NFS4 has created issues in the past) as well as a new clean install VM that was not imported from VMware and see if the issue persists.

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