Backup Error: Failed to flush buffer to this destination

May 16, 2025

Product Version

AhsayACB / AhsayOBM: 7.9.2.0 or above

Operating System

All Platforms

Symptom

When performing a backup job of any type, the following error is received in the backup log:

No.TypeTimestampLog
*.........
*info......
*erroYYYY/MM/DD hh:mm:ssError="ChunkedOutputStream.FlushData.execute]
Failed to flush buffer
(directory_path\vm_name-flat.vmdk)
to this destination.
Error='java.io.IOException:
[FastPipedOutputStream.write]
FastPipedOutputStream has
been closed by the reading thread.',
caused by [IOException]
[FastPipedOutputStream.write]
FastPipedOutputStream has
been closed by the reading thread."
*.........

Cause

This issue is caused by an unstable network connection between the AhsayOBM / ACB client machine and the backup destination (e.g. AhsayCBS server or Cloud storage service).

Resolution

Please try tuning the timeout and retry parameters on AhsayOBM / ACB to workaround the unstable network connection issue. Increase the number of retry and or read timeout value, this can be done by editing the ${OBC_Install_Home}\afc.opt file.

Parameter Description:

  • com.ahsay.afc.bfs.cloud.ChunkedOutputStream.retry

    The number of times AhsayOBM / ACB would retry to send a block to the backup destination. The default value for retry 10 times.

  • com.ahsay.afc.io.ReadAheadInputStream.timeout

    The read timeout interval before AhsayOBM / ACB retry to send a block to the backup destination. The default timeout value is 90 minutes.

  • com.ahsay.afc.bfs.cloud.ChunkedOutputStream.upperSleepLimit

    The default maximum sleep interval value is 16 minutes.

    If the data block upload fails, then AhsayOBM / ACB will sleep for (30 sec) x 2 ^ (no. of retry - 1) minutes and then try to re-upload the data block again, the maximum sleeping interval is 16 minutes (e.g. 960 seconds), for example 30 sec, 60 sec, 120 sec, 240 sec, 480 sec, 960 sec, 960 sec, 960 sec, 960 sec, 960 sec ... etc).

On the AhsayOBM / ACB client computer:

  1. Browse to the ${OBC_Install_Home} folder.
  2. Edit the afc.opt file.

  3. Add the following values to the afc.opt file.

    Recommended values:

    com.ahsay.afc.bfs.cloud.ChunkedOutputStream.retry=20
com.ahsay.afc.io.ReadAheadInputStream.timeout=300
com.ahsay.afc.bfs.cloud.ChunkedOutputStream.upperSleepLimit=5
  4. Save the file.
  5. Run the backup job again.
Troubleshooting