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File backup failure with "unable to flush I/O writes"
  • Martin W
    0
    I am testing/evaluating the MS SQL Server version of Cloudberry Backup, so I'm posting this here, although it seems likely this is not specific to that version.

    My file backup job failed with the following error:
    Your backup plan *{plan name clipped}* COMPLETED WITH WARNINGS, please see below for more details.

    ERROR: The system was unable to flush I/O writes. This can be a transient problem. It is recommended to wait ten minutes and try again, up to three times.

    I have several questions and comments:
    • First, any insight into what is causing this error and how to resolve it? From a Google search, it appears that it has something to do with the VSS (Volume Shadow Copy) service. (In the backup job, the "Use system VSS provider" option is not checked.)
    • Second, is there any way to configure a retry of the backup job when this error occurs? I did not see an option to do so.
    • This is reported as a "Warning." However, zero files were backed up! It seems like this should be categorized as an error.

    Thanks for your help!
    Martin W Options
  • David Gugick
    118
    ↪Martin W
    If you’re not backing up any applications that use their own VSS provider, then consider selecting to use the System VSS Provider. I’m assuming the SQL Server databases files are not selected in this plan.
    David Gugick Options
  • Martin W
    0
    Thanks David. The same error did not occur on the following night's backup, so the backup completed successfully. I also changed the option to "use system VSS provider" as you suggested. However, I'm still interested to know if there is a "retry" option when such errors occur. Waiting 24 hours to retry the backup puts files not backed up at risk. At the same time, I don't want to retry the backup during the day when I see the email that the backup has failed.
    Martin W Options
  • Matt
    91
    ↪Martin W
    The software actually uses automatic retry system as long as your system allows to perform such operations. I/O errors are tricky to avoid, since they happen outside of the software, so in some cases it's difficult to avoid situations like that.
    Matt Options
  • Martin W
    0
    Hi Matt,
    From what I can see in the Windows Event Log, it looks like there may be a bug in Cloudberry Backup. I am submitting an issue report with the details. I'd appreciate your quick follow up and response there. I'd like to switch to Cloudberry, but this is a show stopper.
    thanks,
    Martin
    Martin W Options
  • Martin W
    0
    I should add that the problem recurred last night, even though I switched to "use system VSS provider."
    Martin W Options
  • Martin W
    0
    The backup has run successfully nightly for the past 4 nights... just an update.
    Martin W Options
  • Matt
    91
    ↪Martin W
    Thanks for the update.I suggest to continue communication in the ticket if the issue persists and re-send us the logs.
    Matt Options
  • Jason Lawrence
    0
    ↪Martin W
    If you are facing “File backup failure with "unable to flush I/O” issue then this error may be as a result of an issue with the VSS subsystem on the Agent machine or Hyper-V host caused by VSS not being able to quiesce data to the disk within the VSS timeout window. And the solution is to switch to “use system VSS provider.".
    Jason Lawrence Options
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