Backup to remote FTP server fails: Curl error: Unable to resume an interrupted upload: (55) Failed sending data to the peer

Gabriel Aznarez

Updated May 11, 2023 19:18

Plesk for Windows Plesk for Linux kb: technical ABT: Group A

Applicable to:

Plesk for Linux
Plesk for Windows

Symptoms

A Plesk Backup to remote FTP server fails with one of the following errors:

CONFIG_TEXT: Error: server "server"
Curl error: Unable to resume an interrupted upload: (55) Failed sending data to the peer: Last FTP request: APPE backup_1801300838.zip: Last FTP response: 150 Opening BINARY mode data connection for backup_1801300838.zip: Connection to the FTP server has lost

CONFIG_TEXT: Unable to create remote backup. Error: Unable to export backup: Curl error: Unable to resume an interrupted upload: (55) Failed sending data to the peer: Last FTP request: APPE backup_2008150549.tar: Last FTP response: 150 Accepted data connection: Connection to the FTP server has lost

CONFIG_TEXT: Unable to create the remote backup: Curl error: Unable to resume an interrupted upload: (55) Failed sending data to the peer: Last FTP request: APPE backup_1801300838.zip64: Last FTP response: 125 Data connection already open; Transfer starting: Connection to the FTP server has lost

The following error can be found in the /var/log/plesk/PMM/backup-YYYY-DD-MM-hh-mm-ss-xxx/backup.log file:

PLESK_INFO: INFO: Unable to resume interrupted upload[1a23b456-1a2b-1234-12a3-a1b2c456d789]: Unable to resume an interrupted upload. It seems like FTP server deleted the file, when the connection was lost. Try to repeat or perform upload manually: The connectivity problem: (55) Failed sending data to the peer: Last FTP request: STOR backup_YYMMDDhhmm.tar: Last FTP response: 150 Opening BINARY mode data connection for backup_YYMMDDhhmm.tar [:0]
If the option Save backups in the server storage if the upload to FTP fails is enabled at Tools & Settings > Backup Manager > Settings the locally created backup can contain the following multiple warning:

PLESK_INFO: [WARNING]: Cannot dump domain hosting content [Curl error: Unable to resume an interrupted upload: (55) Failed sending data to the peer: Last FTP request: APPE backup_1801300838.zip: Last FTP response: 150 Opening BINARY mode SSL data connection for 'backup_1801300838.zip': Connection to the FTP server has lost]
The debug log %plesk_dir%\PMM\logs\backup-YYYY-DD-MM-hh-mm-ss-xxx\backupcontains entries about several unsuccessful attempts to resume the FTP connection and upload files:

PLESK_INFO: Debug: Curl error: (55) Failed sending data to the peer: Last FTP request: APPE backup_1801300838.zip: Last FTP response: 150 Opening BINARY mode data connection for backup_1801300838.zip
Debug: Pause before next attempt to upload file...
Debug: Trying to resume upload...

Cause

The FTP server or FTP user exceeded quotas or limits, e.g hard disk quota, in the middle of the backup process.

Resolution

Check and adjust the limits and quotas for the FTP server and user.

Note: if this limit is a FTP timeout, it is possible to avoid this issue by enabling multivolume backup in Tools & Settings > Backup Manager > Schedule > Create a multivolume backup, volume size (MB).