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

Last update: 15-02-2022


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

The main reason of this error is that network connection timed out and Windows does not retry it. Possible corrective measures:

  1. Update drivers for the network adapter(s)
  2. Temporarily disable Firewalls and anti-virus software
  3. Verify connection to Acronis servers with Connection Verification Tool: see this article for instructions.

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 Support with the following information: