vCenter VAMI Backups to SFTP Share Fail with curl: (79) Error in the SSH layer Due to SFTP User Quota

Products

• VMware vCenter Server

Issue/Introduction

Automated or manual backups initiated from the vCenter Server Management Interface (VAMI) to an SFTP destination fail consistently.

Testing the connection via the vCenter SSH console using the backup account succeeds (the user is able to connect, create, and delete small test files without issue). However, the actual backup workflow fails.

The /var/log/vmware/applmgmt/backup.log shows the following errors during the backup of large components (such as StellarDb, VCDB, and ComponentScripts):

 [20260408-180004-24853646] [StellarDbBackup:PID-186243] [Proc::GetProcsStatus:Proc.py:328] ERROR: rc: 2, stderr: /usr/bin/tar: -: Wrote only 6144 of 10240 bytes
/usr/bin/tar: Error is not recoverable: exiting now
...
  File "/usr/lib/applmgmt/backup_restore/py/vmware/appliance/backup_restore/plugins/../util/Calculate.py", line 45, in main
    stdout_obj.write(data)
BrokenPipeError: [Errno 32] Broken pipe
...
 [20260408-180004-24853646] [StellarDbBackup:PID-186243] [Proc::GetProcsStatus:Proc.py:361] ERROR: rc: 79, stderr: b'curl: (79) Error in the SSH layer\n'
...
util.Common.BackupRestoreError: Failed to backup Stellar DB
Underlying process status. rc: 79
stdout:
stderr: b'curl: (79) Error in the SSH layer\n'
...
 [20260408-180004-24853646] [MainProcess:PID-185910] [Proc::VerifyProcStatusAndGetArchive:Proc.py:163] ERROR: stderr:Failed configuration files backup
b'curl: (79) Error in the SSH layer\n'

Environment

vCenter Server Appliance 8.x

Cause

The backup user account has hit its configured storage user quota on the destination SFTP server.

While the user has enough permissions and space to create a small, zero-byte test file via an interactive SSH session (which gives a false positive that the connection is perfectly healthy), the actual backup payload contains large, compressed databases. When the transfer of these large files exceeds the account's strict storage quota limit, the SFTP server forcibly drops the connection. This sudden drop surfaces as a generic Broken pipe and curl: (79) Error in the SSH layer on the vCenter side.

Resolution

To resolve this issue, work with the storage or system administrator to increase or completely remove the user quota limit for the specific backup account on the destination SFTP server.

Ensuring adequate allocated space allows vCenter to complete the transfer of the full, compressed backup payload without the SFTP server terminating the connection prematurely.

Additional Information

The symptom and log entries for this issue are identical to the SSH connection timeout issue described in Broadcom KB 412555 (VAMI backups fail intermittently when Supervisor Control Plane is included). However, the root cause is distinct (Hard Storage Quota vs. Idle Session Timeout).

Reference:VAMI backups fail intermittently when Supervisor Control Plane is included.