Troubleshooting Storage Vault connection errors (wsarecv / Connection forcibly closed) in Comet Backup

Symptoms

When running backup jobs targeting network-accessible Storage Vaults, the job returns with a TCP warning. The error log typically contains details similar to:

CONFIG_TEXT: Can't access Storage Vault: read tcp: wsarecv: An existing connection was forcibly closed by the remote host.

There may be more text in the warning, depending on the Storage Vault type.

Cause

A wsarecv warning indicating a connection was "forcibly closed by the remote host" means that the network socket between the Comet Backup agent and the storage server was abruptly terminated.

This is usually caused by the storage platform itself, or by a 'man-in-the-middle proxy or firewall. Most often intermittent connection drops due to high load on the storage server. Network configuration, hardware, or security software between the agent and the storage server can also cause this.

Resolution

Where possible, retrieve logs from the storage platform (via its dashboard or support channel) to check for connection drops, throttling, or rate-limiting around the time of the failed backup job. This helps confirm whether the storage server is the source of the interruption.

It is likely that the storage server is dropping the connection due to high IO load. Space out concurrent backups or set a speed limit on the backup schedule, or custom backup, to reduce the load.

Speed limits can be set in the schedule or custom backup dialog, on the advanced tabs.