46735: Acronis Cyber Backup: Backup Fails with 'The semaphore timeout period has expired'

Last update: 29-04-2021

Proceed as described in http://support.microsoft.com/kb/325487 and http://support.microsoft.com/kb/892100/en-us


The error message "the semaphore timeout period has expired" can occur in different situations:

  • during backup when Acronis Cyber Backup is actively writing files to a network storage
  • during backup or replication to tape


'The semaphore timeout period has expired' is a network and in some situations a tape hardware error.


Backup to network storage

Microsoft has published a detailed Knowledge Base article available at http://support.microsoft.com/kb/325487 that discusses this particular error and a series of related messages. If you are encountering this message we recommend working through this article.

The following Microsoft KB article can also be helpful if you’re experiencing "the semaphore timeout period has expired" and the system in question is running Windows 2003: The processor load is not distributed across multiple processors on a computer that is running Windows Server 2003, Windows 2000 server, or Windows NT 4.0.

Backup to tape

In case the error occurs during backup or replication to tape, usually, a Semaphore Timeout error can be associated to the tape drivers, defective SAN switches or other interfaces used for tape connection. Please ensure that hardware is working without errors, updade tape drivers and Acronis software and make sure writing to tape with original Tape Tools (provided by your manufacturer: HP, Dell etc.) does not produce the same error. Otherwise, contact the manufacturer.

More information

If these instructions do not help, please contact Acronis Customer Central with the following information: