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Issue Plesk Backup Aborts at ~128 GB Uploading to FTP (Curl Error 55)

audiobras

New Pleskian
Server operating system version
AlmaLinux 9.5 (Teal Serval) and Centos 7 in ftp server
Plesk version and microupdate number
18.0.68 #2
Hello Plesk Community,

I’m encountering a problem when sending full-server backups from my Plesk panel to a remote FTP server. The transfer always stops at approximately 128.79 GB, with a steady upload speed (~109–110 MB/s), and Plesk logs the following error:

Unable to create the remote backup:
Curl error: Unable to resume an interrupted upload: (55) Failed sending data to the peer

In the /var/log/xferlog, each attempt shows the file marked as “i” (incomplete), and only a few kilobytes are ever retried before Plesk aborts and deletes the partial archive. Example excerpt:

Fri Mar 28 02:34:40 2025 1167 xxxxxxxx 128789846920 /xxxxx/backup_2503272315.tar b _ i r rootftp ftp 0 * i
Fri Mar 28 02:34:44 2025 1 xxxxxxxx 14480 /xxxxxx/backup_2503272315.tar b _ i r rootftp ftp 0 * i

...

In my panel.ini, I’ve set:
streamCacheSize = 1024
ftpMaxResumeAttempts = 10
ftpMaxResumeFailures = 15
ftpFileTransferTimeout = 36000
ftpForbidReuseConnection = 1
backupsValidationPeriod = 0

What I’ve tried so far:
  1. Adjusted streamCacheSize in panel.ini (currently 1024) to increase buffer, without success.
  2. Verified network stability—no packet loss or obvious timeouts on my side.
  3. Confirmed the partial file is always purged by Plesk immediately after the abort.
Questions
  1. Could any of these settings be causing the backup to abort at ~128 GB?
  2. What quick configuration tweaks or tests can I try—either in Plesk or on the FTP server—to allow the backup to complete?

Thanks in advance for any pointers!

Delton
 
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