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#1 2022-12-25 14:55:22

wimg
Member
Registered: 2020-01-09
Posts: 21

"The CBT sequence has not changed since last backup" on every backup

We're seeing something very troubling. Every backup says (on every .vmdk file) : "The CBT sequence has not changed since last backup"

Our command is :
  /scratch/XSI/XSIBackup-DC/xsibackup \
    --replica=cbt \
    "VMs(clientname)" \
    /destination/clientname \
    --backup-how="hot" \
    --config-backup \
    --quiesce \
    --rotate="5D"

Anyone have any idea what might be causing this ?

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#2 2022-12-29 11:10:56

admin
Administrator
Registered: 2017-04-21
Posts: 2,019

Re: "The CBT sequence has not changed since last backup" on every backup

Sorry about the delay.

Well, we would need to know the context. That notice may very well just mean what it says. You will get that on a stopped VM per instance. Or maybe for some reason the -ctk.vmdk files are not being updated. Contact support if you believe you face some kind of trouble.

UPDATE:

We have conducted a number of tests and we were able to reproduce your reported behaviour to some extent. We are working on it and will post back here when we are done and know exactly what is going on.

To make sure that you copy all your data we suggest that you do a full checksum based backup by removing the cbt flag.

UPDATE:

Your reported behaviour can occur if you keep a snapshot on the VM being CBT backed up. This may be a bug in 1.6.0.1, as when using CBT ©XSIBackup should delete any previously existing snapshot. We'll delve on the issue and eventually release a fix as 1.6.0.2.

In any case, if that is your case (you have some snapshot), the notice is correct and the new data is being saved to the snapshot file, thus we still have to determine whether this should be considered a bug and ©XSIBackup should delete any previously existing snapshot, or on the contrary could be considered just normal behaviour, as your data would be commited to the base disks and copied by CBT once you commit that snapshot to the base disks.

On top of that, the snapshot containing the new data would be copied along with the rest of the VM files, thus you would indeed be backing up everything you need.

CONCLUSION:

In the end, after some through inspection, we didn't detect any anomalous behaviour. Below we dissect the matter up so that you can make your own assesment. Of course this does not exclude the possibility of some more complex issue on your side, still we have very limited information from your part.

We'll stick to --replica action which is what you reported. In this case all snapshots are indeed deleted when the =cbt flag is used, this is working fine as per our tests. Thus, if you are still getting "The CBT sequence has not changed since last backup" message, the possibilities are:

1/ The VM is off. Too obvious, but has to be on the list.
2/ The VM didn't change indeed. This is rare, as at least some logs will be updated every few minutes, but can happen in some OSs. We have been able to corroborate that in some CentOS 6 VMs, the -ctk.vmdk files aren't updated even after taking a new backup snapshot during a rather long period of time.
3/ The -ctk.vmdk files were imported/moved with the VM from a different host but the --reset-cbt argument wasn't run.
4/ The CBT feature isn't working right in the ESXi host.

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